Saint Peter's Basilica
Saint Peter's Basilica
St. Peter's is a church in the Renaissance style located in the Vatican City west of the River Tiber and near the Janiculum Hill and Hadrian's Mausoleum. Its central dome dominates the skyline of Rome. The basilica is approached via St. Peter's Square, a forecourt in two sections, both surrounded by tall colonnades. The first space is oval and the second trapezoid. The façade of the basilica, with a giant order of columns, stretches across the end of the square and is approached by steps on which stand two 5.55 metres (18.2 ft) statues of the 1st-century apostles to Rome, Saints Peter and Paul.
The basilica is cruciform in shape, with an elongated nave in the Latin cross form but the early designs were for a centrally planned structure and this is still in evidence in the architecture. The central space is dominated both externally and internally by one of the largest domes in the world. The entrance is through a narthex, or entrance hall, which stretches across the building. One of the decorated bronze doors leading from the narthex is the Holy Door, only opened during jubilees.
The nave which leads to the central dome is in three bays, with piers supporting a barrel-vault, the highest of any church. The nave is framed by wide aisles which have a number of chapels off them. There are also chapels surrounding the dome. Moving around the basilica in a clockwise direction they are: The Baptistery, the Chapel of the Presentation of the Virgin, the larger Choir Chapel, the Clementine Chapel with the altar of Saint Gregory, the Sacristy Entrance, the left transept with altars to the Crucifixion of Saint Peter, Saint Joseph and Saint Thomas, the altar of the Sacred Heart, the Chapel of the Madonna of Colonna, the altar of Saint Peter and the Paralytic, the apse with the Chair of Saint Peter, the altar of Saint Peter raising Tabitha, the altar of the Archangel Michael, the altar of the Navicella, the right transept with altars of Saint Erasmus, Saints Processo and Martiniano, and Saint Wenceslas, the altar of Saint Basil, the Gregorian Chapel with the altar of the Madonna of Succour, the larger Chapel of the Holy Sacrament, the Chapel of Saint Sebastian and the Chapel of the Pietà.[9] At the heart of the basilica, beneath the high altar, is the Confessio or Chapel of the Confession, in reference to the confession of faith by St. Peter, which led to his martyrdom. Two curving marble staircases lead to this underground chapel at the level of the Constantinian church and immediately above the purported burial place of Saint Peter.
The entire interior of St. Peter's is lavishly decorated with marble, reliefs, architectural sculpture and gilding. The basilica contains a large number of tombs of popes and other notable people, many of which are considered outstanding artworks. There are also a number of sculptures in niches and chapels, including Michelangelo's Pietà. The central feature is a baldachin, or canopy over the Papal Altar, designed by Gian Lorenzo Bernini. The sanctuary culminates in a sculptural ensemble, also by Bernini, and containing the symbolic Chair of Saint Peter.
Successive plan
Pope Julius' scheme for the grandest building in Christendom was the subject of a competition for which a number of entries remain intact in the Uffizi Gallery, Florence. It was the design of Donato Bramante that was selected, and for which the foundation stone was laid in 1506. This plan was in the form of an enormous Greek Cross with a dome inspired by that of the huge circular Roman temple, the Pantheon. The main difference between Bramante's design and that of the Pantheon is that where the dome of the Pantheon is supported by a continuous wall, that of the new basilica was to be supported only on four large piers. This feature was maintained in the ultimate design. Bramante's dome was to be surmounted by a lantern with its own small dome but otherwise very similar in form to the Early Renaissance lantern of Florence Cathedral designed for Brunelleschi's dome by Michelozzo.
Bramante had envisioned that the central dome be surrounded by four lower domes at the diagonal axes. The equal chancel, nave and transept arms were each to be of two bays ending in an apse. At each corner of the building was to stand a tower, so that the overall plan was square, with the apses projecting at the cardinal points. Each apse had two large radial buttresses, which squared off its semi-circular shape.
When Pope Julius died in 1513, Bramante was replaced with Giuliano da Sangallo, Fra Giocondo and Raphael. Sangallo and Fra Giocondo both died in 1515, Bramante himself having died the previous year. The main change in Raphael's plan is the nave of five bays, with a row of complex apsidal chapels off the aisles on either side. Raphael's plan for the chancel and transepts made the squareness of the exterior walls more definite by reducing the size of the towers, and the semi-circular apses more clearly defined by encircling each with an ambulatory.
In 1520 Raphael also died, aged 37, and his successor Baldassare Peruzzi maintained changes that Raphael had proposed to the internal arrangement of the three main apses, but otherwise reverted to the Greek Cross plan and other features of Bramante. This plan did not go ahead because of various difficulties of both Church and state. In 1527 Rome was sacked and plundered by Emperor Charles V. Peruzzi died in 1536 without his plan being realized.
At this point Antonio da Sangallo the Younger submitted a plan which combines features of Peruzzi, Raphael and Bramante in its design and extends the building into a short nave with a wide façade and portico of dynamic projection. His proposal for the dome was much more elaborate of both structure and decoration than that of Bramante and included ribs on the exterior. Like Bramante, Sangallo proposed that the dome be surmounted by a lantern which he redesigned to a larger and much more elaborate form. Sangallo's main practical contribution was to strengthen Bramante's piers which had begun to crack.
On 1 January 1547 in the reign of Pope Paul III, Michelangelo, then in his seventies, succeeded Sangallo the Younger as "Capomaestro", the superintendent of the building program at St Peter's. He is to be regarded as the principal designer of a large part of the building as it stands today, and as bringing the construction to a point where it could be carried through. He did not take on the job with pleasure; it was forced upon him by Pope Paul, frustrated at the death of his chosen candidate, Giulio Romano and the refusal of Jacopo Sansovino to leave Venice. Michelangelo wrote "I undertake this only for the love of God and in honour of the Apostle." He insisted that he should be given a free hand to achieve the ultimate aim by whatever means he saw fit.
Michelangelo's contribution
Michelangelo took over a building site at which four piers, enormous beyond any constructed since ancient Roman times, were rising behind the remaining nave of the old basilica. He also inherited the numerous schemes designed and redesigned by some of the greatest architectural and engineering minds of the 16th century. There were certain common elements in these schemes. They all called for a dome to equal that engineered by Brunelleschi a century earlier and which has since dominated the skyline of Renaissance Florence, and they all called for a strongly symmetrical plan of either Greek Cross form, like the iconic St. Mark's Basilica in Venice, or of a Latin Cross with the transepts of identical form to the chancel, as at Florence Cathedral.
Even though the work had progressed only a little in 40 years, Michelangelo did not simply dismiss the ideas of the previous architects. He drew on them in developing a grand vision. Above all, Michelangelo recognized the essential quality of Bramante's original design.
As it stands today, St. Peter's has been extended with a nave by Carlo Maderno. It is the chancel end (the ecclesiastical "Eastern end") with its huge centrally placed dome that is the work of Michelangelo. Because of its location within the Vatican State and because the projection of the nave screens the dome from sight when the building is approached from the square in front of it, the work of Michelangelo is best appreciated from a distance. What becomes apparent is that the architect has greatly reduced the clearly defined geometric forms of Bramante's plan of a square with square projections, and also of Raphael's plan of a square with semi-circular projections. Michelangelo has blurred the definition of the geometry by making the external masonry of massive proportions and filling in every corner with a small vestry or stairwell. The effect created is of a continuous wall-surface that is folded or fractured at different angles, but lacks the right-angles which usually define change of direction at the corners of a building. This exterior is surrounded by a giant order of Corinthian pilasters all set at slightly different angles to each other, in keeping with the ever-changing angles of the wall's surface. Above them the huge cornice ripples in a continuous band, giving the appearance of keeping the whole building in a state of compression.
Dome: successive and final design
The dome of St. Peter's rises to a total height of 136.57 metres (448.1 ft) from the floor of the basilica to the top of the external cross. It is the tallest dome in the world. Its internal diameter is 41.47 metres (136.1 ft), slightly smaller than two of the three other huge domes that preceded it, those of the Pantheon of Ancient Rome, 43.3 metres (142 ft), and Florence Cathedral of the Early Renaissance, 44 metres (144 ft). It has a greater diameter by approximately 30 feet (9.1 m) than Constantinople's Hagia Sophia church, completed in 537. It was to the domes of the Pantheon and Florence duomo that the architects of St. Peter's looked for solutions as to how to go about building what was conceived, from the outset, as the greatest dome of Christendom.
Bramante and Sangallo, 1506 and 1513
The dome of the Pantheon stands on a circular wall with no entrances or windows except a single door. The whole building is as high as it is wide. Its dome is constructed in a single shell of concrete, made light by the inclusion of a large amount of the volcanic stones tuff and pumice. The inner surface of the dome is deeply coffered which has the effect of creating both vertical and horizontal ribs, while lightening the overall load. At the summit is an ocular opening 8 metres (26 ft) across which provides light to the interior.
Bramante's plan for the dome of St. Peter's (1506) follows that of the Pantheon very closely, and like that of the Pantheon, was designed to be constructed in Tufa Concrete for which he had rediscovered a formula. With the exception of the lantern that surmounts it, the profile is very similar, except that in this case the supporting wall becomes a drum raised high above ground level on four massive piers. The solid wall, as used at the Pantheon, is lightened at St. Peter's by Bramante piercing it with windows and encircling it with a peristyle.
In the case of Florence Cathedral, the desired visual appearance of the pointed dome existed for many years before Brunelleschi made its construction feasible.[39] Its double-shell construction of bricks locked together in herringbone pattern (re-introduced from Byzantine architecture), and the gentle upward slope of its eight stone ribs made it possible for the construction to take place without the massive wooden formwork necessary to construct hemispherical arches. While its appearance, with the exception of the details of the lantern, is entirely Gothic, its engineering was highly innovative, and the product of a mind that had studied the huge vaults and remaining dome of Ancient Rome.
Sangallo's plan (1513), of which a large wooden model still exists, looks to both these predecessors. He realised the value of both the coffering at the Pantheon and the outer stone ribs at Florence Cathedral. He strengthened and extended the peristyle of Bramante into a series of arched and ordered openings around the base, with a second such arcade set back in a tier above the first. In his hands, the rather delicate form of the lantern, based closely on that in Florence, became a massive structure, surrounded by a projecting base, a peristyle and surmounted by a spire of conic form
Michelangelo and Giacomo della Porta, 1547 and 1585
Michelangelo redesigned the dome in 1547, taking into account all that had gone before. His dome, like that of Florence, is constructed of two shells of brick, the outer one having 16 stone ribs, twice the number at Florence but far fewer than in Sangallo's design. As with the designs of Bramante and Sangallo, the dome is raised from the piers on a drum. The encircling peristyle of Bramante and the arcade of Sangallo are reduced to 16 pairs of Corinthian columns, each of 15 metres (49 ft) high which stand proud of the building, connected by an arch. Visually they appear to buttress each of the ribs, but structurally they are probably quite redundant. The reason for this is that the dome is ovoid in shape, rising steeply as does the dome of Florence Cathedral, and therefore exerting less outward thrust than does a hemispherical dome, such as that of the Pantheon, which, although it is not buttressed, is countered by the downward thrust of heavy masonry which extends above the circling wall.
The ovoid profile of the dome has been the subject of much speculation and scholarship over the past century. Michelangelo died in 1564, leaving the drum of the dome complete, and Bramante's piers much bulkier than originally designed, each 18 metres (59 ft) across. Following his death, the work continued under his assistant Jacopo Barozzi da Vignola with Giorgio Vasari appointed by Pope Pius V as a watchdog to make sure that Michelangelo's plans were carried out exactly. Despite Vignola's knowledge of Michelangelo's intentions, little happened in this period. In 1585 the energetic Pope Sixtus appointed Giacomo della Porta who was to be assisted by Domenico Fontana. The five-year reign of Sixtus was to see the building advance at a great rate.
Michelangelo left a few drawings, including an early drawing of the dome, and some drawings of details. There were also detailed engravings published in 1569 by Stefan du Pérac who claimed that they were the master's final solution. Michelangelo, like Sangallo before him, also left a large wooden model. Giacomo della Porta subsequently altered this model in several ways, in keeping with changes that he made to the design. Most of these changes were of a cosmetic nature, such as the adding of lion's masks over the swags on the drum in honour of Pope Sixtus and adding a circlet of finials around the spire at the top of the lantern, as proposed by Sangallo. The major change that was made to the model, either by della Porta, or Michelangelo himself before his death, was to raise the outer dome higher above the inner one.
A drawing by Michelangelo indicates that his early intentions were towards an ovoid dome, rather than a hemispherical one. In an engraving in Galasso Alghisi' treatise (1563), the dome may be represented as ovoid, but the perspective is ambiguous. Stefan du Pérac's engraving (1569) shows a hemispherical dome, but this was perhaps an inaccuracy of the engraver. The profile of the wooden model is more ovoid than that of the engravings, but less so than the finished product. It has been suggested that Michelangelo on his death bed reverted to the more pointed shape. However Lees-Milne cites Giacomo della Porta as taking full responsibility for the change and as indicating to Pope Sixtus that Michelangelo was lacking in the scientific understanding of which he himself was capable.
Helen Gardner suggests that Michelangelo made the change to the hemispherical dome of lower profile in order to establish a balance between the dynamic vertical elements of the encircling giant order of pilasters and a more static and reposeful dome. Gardner also comments "The sculpturing of architecture [by Michelangelo]... here extends itself up from the ground through the attic stories and moves on into the drum and dome, the whole building being pulled together into a unity from base to summit."
It is this sense of the building being sculptured, unified and "pulled together" by the encircling band of the deep cornice that led Eneide Mignacca to conclude that the ovoid profile, seen now in the end product, was an essential part of Michelangelo's first (and last) concept. The sculptor/architect has, figuratively speaking, taken all the previous designs in hand and compressed their contours as if the building were a lump of clay. The dome must appear to thrust upwards because of the apparent pressure created by flattening the building's angles and restraining its projections.If this explanation is the correct one, then the profile of the dome is not merely a structural solution, as perceived by Giacomo della Porta; it is part of the integrated design solution that is about visual tension and compression. In one sense, Michelangelo's dome may appear to look backward to the Gothic profile of Florence Cathedral and ignore the Classicism of the Renaissance, but on the other hand, perhaps more than any other building of the 16th century, it prefigures the architecture of the Baroque
Completion
The dome was brought to completion by Giacomo della Porta and Fontana.
Giacomo della Porta and Domenico Fontana brought the dome to completion in 1590, the last year of the reign of Sixtus V. His successor, Gregory XIV, saw Fontana complete the lantern and had an inscription to the honour of Sixtus V placed around its inner opening. The next pope, Clement VIII, had the cross raised into place, an event which took all day, and was accompanied by the ringing of the bells of all the city's churches. In the arms of the cross are set two lead caskets, one containing a fragment of the True Cross and a relic of St. Andrew and the other containing medallions of the Holy Lamb.
In the mid 18th century, cracks appeared in the dome, so four iron chains were installed between the two shells to bind it, like the rings that keep a barrel from bursting. As many as ten chains have been installed at various times, the earliest possibly planned by Michelangelo himself as a precaution, as Brunelleschi did at Florence Cathedral.
Changes of plan
On 18 February 1606, under Pope Paul V, the dismantling of the remaining parts of the Constantinian basilica began. The marble cross that had been set at the top of the pediment by Pope Sylvester and Constantine the Great was lowered to the ground. The timbers were salvaged for the roof of the Borghese Palace and two rare black marble columns, the largest of their kind, were carefully stored and later used in the narthex. The tombs of various popes were opened, treasures removed and plans made for reinterment in the new basilica.
The Pope had appointed Carlo Maderno in 1602. He was a nephew of Domenico Fontana and had demonstrated himself as a dynamic architect. Maderno's idea was to ring Michelangelo's building with chapels, but the Pope was hesitant about deviating from the master's plan, even though he had been dead for forty years. The Fabbrica or building committee, a group drawn from various nationalities and generally despised by the Curia who viewed the basilica as belonging to Rome rather than Christendom, were in a quandary as to how the building should proceed. One of the matters that influenced their thinking was the Counter-Reformation which increasingly associated a Greek Cross plan with paganism and saw the Latin Cross as truly symbolic of Christianity.
Another influence on the thinking of both the Fabbrica and the Curia was a certain guilt at the demolition of the ancient building. The ground on which it and its various associated chapels, vestries and sacristies had stood for so long was hallowed. The only solution was to build a nave that encompassed the whole space. In 1607 a committee of ten architects was called together, and a decision was made to extend Michelangelo's building into a nave. Maderno's plans for both the nave and the façade were accepted. The building began on 7 May 1607, and proceeded at a great rate, with an army of 700 labourers being employed. The following year, the façade was begun, in December 1614 the final touches were added to the stucco decoration of the vault and early in 1615 the partition wall between the two sections was pulled down. All the rubble was carted away, and the nave was ready for use by Palm Sunday.
Maderno's façade
The façade designed by Maderno, is 114.69 metres (376.3 ft) wide and 45.55 metres (149.4 ft) high and is built of travertine stone, with a giant order of Corinthian columns and a central pediment rising in front of a tall attic surmounted by thirteen statues: Christ flanked by eleven of the Apostles (except Peter, whose statue is left of the stairs) and John the Baptist.
The façade is often cited as the least satisfactory part of the design of St. Peter's. The reasons for this, according to James Lees-Milne, are that it was not given enough consideration by the Pope and committee because of the desire to get the building completed quickly, coupled with the fact that Maderno was hesitant to deviate from the pattern set by Michelangelo at the other end of the building. Lees-Milne describes the problems of the façade as being too broad for its height, too cramped in its details and too heavy in the attic storey. The breadth is caused by modifying the plan to have towers on either side. These towers were never executed above the line of the façade because it was discovered that the ground was not sufficiently stable to bear the weight. One effect of the façade and lengthened nave is to screen the view of the dome, so that the building, from the front, has no vertical feature, except from a distance.
Maderno's nave
To the single bay of Michelangelo's Greek Cross, Maderno added a further three bays. He made the dimensions slightly different from Michelangelo's bay, thus defining where the two architectural works meet. Maderno also tilted the axis of the nave slightly. This was not by accident, as suggested by his critics. An ancient Egyptian obelisk had been erected in the square outside, but had not been quite aligned with Michelangelo's building, so Maderno compensated, in order that it should, at least, align with the Basilica's façade.
The nave has huge paired pilasters, in keeping with Michelangelo's work. The size of the interior is so "stupendously large" that it is hard to get a sense of scale within the building. The four cherubs who flutter against the first piers of the nave, carrying between them two holy water basins, appear of quite normal cherubic size, until approached. Then it becomes apparent that each one is over 2 metres high and that real children cannot reach the basins unless they scramble up the marble draperies. The aisles each have two smaller chapels and a larger rectangular chapel, the Chapel of the Sacrament and the Choir Chapel. These are lavishly decorated with marble, stucco, gilt, sculpture and mosaic. Remarkably, there are very few paintings, although some, such as Raphael's "Sistine Madonna" have been reproduced in mosaic. The most precious painting is a small icon of the Madonna, removed from the old basilica.
Maderno's last work at St. Peter's was to design a crypt-like space or "Confessio" under the dome, where the cardinals and other privileged persons could descend in order to be nearer to the burial place of the apostle. Its marble steps are remnants of the old basilica and around its balustrade are 95 bronze lamps.
St. Peter's Piazza
To the east of the basilica is the Piazza di San Pietro, (St. Peter's Square). The present arrangement, constructed between 1656 and 1667, is the Baroque inspiration of Bernini who inherited a location already occupied by an Egyptian obelisk which was centrally placed, (with some contrivance) to Maderno's façade. The obelisk, known as "The Witness", at 25.5 metres (84 ft) and a total height, including base and the cross on top, of 40 metres (130 ft), is the second largest standing obelisk, and the only one to remain standing since its removal from Egypt and re-erection at the Circus of Nero in 37 AD, where it is thought to have stood witness to the crucifixion of St Peter. Its removal to its present location by order of Pope Sixtus V and engineered by Domenico Fontana on 28 September 1586, was an operation fraught with difficulties and nearly ending in disaster when the ropes holding the obelisk began to smoke from the friction. Fortunately this problem was noticed by Benedetto Bresca, a sailor of Sanremo, and for his swift intervention, his town was granted the privilege of providing the palms that are used at the basilica each Palm Sunday.
The other object in the old square with which Bernini had to contend was a large fountain designed by Maderno in 1613 and set to one side of the obelisk, making a line parallel with the façade. Bernini's plan uses this horizontal axis as a major feature of his unique, spatially dynamic and highly symbolic design. The most obvious solutions were either a rectangular piazza of vast proportions so that the obelisk stood centrally and the fountain (and a matching companion) could be included, or a trapezoid piazza which fanned out from the façade of the basilica like that in front of the Palazzo Pubblico in Siena. The problems of the square plan are that the necessary width to include the fountain would entail the demolition of numerous buildings, including some of the Vatican, and would minimise the effect of the façade. The trapezoid plan, on the other hand, would maximise the apparent width of the façade, which was already perceived as a fault of the design.
Bernini's ingenious solution was to create a piazza in two sections. That part which is nearest the basilica is trapezoid, but rather than fanning out from the façade, it narrows. This gives the effect of countering the visual perspective. It means that from the second part of the piazza, the building looks nearer than it is, the breadth of the façade is minimized and its height appears greater in proportion to its width. The second section of the piazza is a huge elliptical circus which gently slopes downwards to the obelisk at its centre. The two distinct areas are framed by a colonnade formed by doubled pairs of columns supporting an entabulature of the simple Tuscan Order.
The part of the colonnade that is around the ellipse does not entirely encircle it, but reaches out in two arcs, symbolic of the arms of "the Catholic Church reaching out to welcome its communicants". The obelisk and Maderno's fountain mark the widest axis of the ellipse. Bernini balanced the scheme with another fountain in 1675. The approach to the square used to be through a jumble of old buildings, which added an element of surprise to the vista that opened up upon passing through the colonnade. Nowadays a long wide street, the Via della Conciliazione, built by Mussolini after the conclusion of the Lateran Treaties, leads from the River Tiber to the piazza and gives distant views of St. Peter's as the visitor approaches.
Bernini's transformation of the site is entirely Baroque in concept. Where Bramante and Michelangelo conceived a building that stood in "self-sufficient isolation", Bernini made the whole complex "expansively relate to its environment".
The basilica is cruciform in shape, with an elongated nave in the Latin cross form but the early designs were for a centrally planned structure and this is still in evidence in the architecture. The central space is dominated both externally and internally by one of the largest domes in the world. The entrance is through a narthex, or entrance hall, which stretches across the building. One of the decorated bronze doors leading from the narthex is the Holy Door, only opened during jubilees.
The nave which leads to the central dome is in three bays, with piers supporting a barrel-vault, the highest of any church. The nave is framed by wide aisles which have a number of chapels off them. There are also chapels surrounding the dome. Moving around the basilica in a clockwise direction they are: The Baptistery, the Chapel of the Presentation of the Virgin, the larger Choir Chapel, the Clementine Chapel with the altar of Saint Gregory, the Sacristy Entrance, the left transept with altars to the Crucifixion of Saint Peter, Saint Joseph and Saint Thomas, the altar of the Sacred Heart, the Chapel of the Madonna of Colonna, the altar of Saint Peter and the Paralytic, the apse with the Chair of Saint Peter, the altar of Saint Peter raising Tabitha, the altar of the Archangel Michael, the altar of the Navicella, the right transept with altars of Saint Erasmus, Saints Processo and Martiniano, and Saint Wenceslas, the altar of Saint Basil, the Gregorian Chapel with the altar of the Madonna of Succour, the larger Chapel of the Holy Sacrament, the Chapel of Saint Sebastian and the Chapel of the Pietà.[9] At the heart of the basilica, beneath the high altar, is the Confessio or Chapel of the Confession, in reference to the confession of faith by St. Peter, which led to his martyrdom. Two curving marble staircases lead to this underground chapel at the level of the Constantinian church and immediately above the purported burial place of Saint Peter.
The entire interior of St. Peter's is lavishly decorated with marble, reliefs, architectural sculpture and gilding. The basilica contains a large number of tombs of popes and other notable people, many of which are considered outstanding artworks. There are also a number of sculptures in niches and chapels, including Michelangelo's Pietà. The central feature is a baldachin, or canopy over the Papal Altar, designed by Gian Lorenzo Bernini. The sanctuary culminates in a sculptural ensemble, also by Bernini, and containing the symbolic Chair of Saint Peter.
Successive plan
Pope Julius' scheme for the grandest building in Christendom was the subject of a competition for which a number of entries remain intact in the Uffizi Gallery, Florence. It was the design of Donato Bramante that was selected, and for which the foundation stone was laid in 1506. This plan was in the form of an enormous Greek Cross with a dome inspired by that of the huge circular Roman temple, the Pantheon. The main difference between Bramante's design and that of the Pantheon is that where the dome of the Pantheon is supported by a continuous wall, that of the new basilica was to be supported only on four large piers. This feature was maintained in the ultimate design. Bramante's dome was to be surmounted by a lantern with its own small dome but otherwise very similar in form to the Early Renaissance lantern of Florence Cathedral designed for Brunelleschi's dome by Michelozzo.
Bramante had envisioned that the central dome be surrounded by four lower domes at the diagonal axes. The equal chancel, nave and transept arms were each to be of two bays ending in an apse. At each corner of the building was to stand a tower, so that the overall plan was square, with the apses projecting at the cardinal points. Each apse had two large radial buttresses, which squared off its semi-circular shape.
When Pope Julius died in 1513, Bramante was replaced with Giuliano da Sangallo, Fra Giocondo and Raphael. Sangallo and Fra Giocondo both died in 1515, Bramante himself having died the previous year. The main change in Raphael's plan is the nave of five bays, with a row of complex apsidal chapels off the aisles on either side. Raphael's plan for the chancel and transepts made the squareness of the exterior walls more definite by reducing the size of the towers, and the semi-circular apses more clearly defined by encircling each with an ambulatory.
In 1520 Raphael also died, aged 37, and his successor Baldassare Peruzzi maintained changes that Raphael had proposed to the internal arrangement of the three main apses, but otherwise reverted to the Greek Cross plan and other features of Bramante. This plan did not go ahead because of various difficulties of both Church and state. In 1527 Rome was sacked and plundered by Emperor Charles V. Peruzzi died in 1536 without his plan being realized.
At this point Antonio da Sangallo the Younger submitted a plan which combines features of Peruzzi, Raphael and Bramante in its design and extends the building into a short nave with a wide façade and portico of dynamic projection. His proposal for the dome was much more elaborate of both structure and decoration than that of Bramante and included ribs on the exterior. Like Bramante, Sangallo proposed that the dome be surmounted by a lantern which he redesigned to a larger and much more elaborate form. Sangallo's main practical contribution was to strengthen Bramante's piers which had begun to crack.
On 1 January 1547 in the reign of Pope Paul III, Michelangelo, then in his seventies, succeeded Sangallo the Younger as "Capomaestro", the superintendent of the building program at St Peter's. He is to be regarded as the principal designer of a large part of the building as it stands today, and as bringing the construction to a point where it could be carried through. He did not take on the job with pleasure; it was forced upon him by Pope Paul, frustrated at the death of his chosen candidate, Giulio Romano and the refusal of Jacopo Sansovino to leave Venice. Michelangelo wrote "I undertake this only for the love of God and in honour of the Apostle." He insisted that he should be given a free hand to achieve the ultimate aim by whatever means he saw fit.
Michelangelo's contribution
Michelangelo took over a building site at which four piers, enormous beyond any constructed since ancient Roman times, were rising behind the remaining nave of the old basilica. He also inherited the numerous schemes designed and redesigned by some of the greatest architectural and engineering minds of the 16th century. There were certain common elements in these schemes. They all called for a dome to equal that engineered by Brunelleschi a century earlier and which has since dominated the skyline of Renaissance Florence, and they all called for a strongly symmetrical plan of either Greek Cross form, like the iconic St. Mark's Basilica in Venice, or of a Latin Cross with the transepts of identical form to the chancel, as at Florence Cathedral.
Even though the work had progressed only a little in 40 years, Michelangelo did not simply dismiss the ideas of the previous architects. He drew on them in developing a grand vision. Above all, Michelangelo recognized the essential quality of Bramante's original design.
As it stands today, St. Peter's has been extended with a nave by Carlo Maderno. It is the chancel end (the ecclesiastical "Eastern end") with its huge centrally placed dome that is the work of Michelangelo. Because of its location within the Vatican State and because the projection of the nave screens the dome from sight when the building is approached from the square in front of it, the work of Michelangelo is best appreciated from a distance. What becomes apparent is that the architect has greatly reduced the clearly defined geometric forms of Bramante's plan of a square with square projections, and also of Raphael's plan of a square with semi-circular projections. Michelangelo has blurred the definition of the geometry by making the external masonry of massive proportions and filling in every corner with a small vestry or stairwell. The effect created is of a continuous wall-surface that is folded or fractured at different angles, but lacks the right-angles which usually define change of direction at the corners of a building. This exterior is surrounded by a giant order of Corinthian pilasters all set at slightly different angles to each other, in keeping with the ever-changing angles of the wall's surface. Above them the huge cornice ripples in a continuous band, giving the appearance of keeping the whole building in a state of compression.
Dome: successive and final design
The dome of St. Peter's rises to a total height of 136.57 metres (448.1 ft) from the floor of the basilica to the top of the external cross. It is the tallest dome in the world. Its internal diameter is 41.47 metres (136.1 ft), slightly smaller than two of the three other huge domes that preceded it, those of the Pantheon of Ancient Rome, 43.3 metres (142 ft), and Florence Cathedral of the Early Renaissance, 44 metres (144 ft). It has a greater diameter by approximately 30 feet (9.1 m) than Constantinople's Hagia Sophia church, completed in 537. It was to the domes of the Pantheon and Florence duomo that the architects of St. Peter's looked for solutions as to how to go about building what was conceived, from the outset, as the greatest dome of Christendom.
Bramante and Sangallo, 1506 and 1513
The dome of the Pantheon stands on a circular wall with no entrances or windows except a single door. The whole building is as high as it is wide. Its dome is constructed in a single shell of concrete, made light by the inclusion of a large amount of the volcanic stones tuff and pumice. The inner surface of the dome is deeply coffered which has the effect of creating both vertical and horizontal ribs, while lightening the overall load. At the summit is an ocular opening 8 metres (26 ft) across which provides light to the interior.
Bramante's plan for the dome of St. Peter's (1506) follows that of the Pantheon very closely, and like that of the Pantheon, was designed to be constructed in Tufa Concrete for which he had rediscovered a formula. With the exception of the lantern that surmounts it, the profile is very similar, except that in this case the supporting wall becomes a drum raised high above ground level on four massive piers. The solid wall, as used at the Pantheon, is lightened at St. Peter's by Bramante piercing it with windows and encircling it with a peristyle.
In the case of Florence Cathedral, the desired visual appearance of the pointed dome existed for many years before Brunelleschi made its construction feasible.[39] Its double-shell construction of bricks locked together in herringbone pattern (re-introduced from Byzantine architecture), and the gentle upward slope of its eight stone ribs made it possible for the construction to take place without the massive wooden formwork necessary to construct hemispherical arches. While its appearance, with the exception of the details of the lantern, is entirely Gothic, its engineering was highly innovative, and the product of a mind that had studied the huge vaults and remaining dome of Ancient Rome.
Sangallo's plan (1513), of which a large wooden model still exists, looks to both these predecessors. He realised the value of both the coffering at the Pantheon and the outer stone ribs at Florence Cathedral. He strengthened and extended the peristyle of Bramante into a series of arched and ordered openings around the base, with a second such arcade set back in a tier above the first. In his hands, the rather delicate form of the lantern, based closely on that in Florence, became a massive structure, surrounded by a projecting base, a peristyle and surmounted by a spire of conic form
Michelangelo and Giacomo della Porta, 1547 and 1585
Michelangelo redesigned the dome in 1547, taking into account all that had gone before. His dome, like that of Florence, is constructed of two shells of brick, the outer one having 16 stone ribs, twice the number at Florence but far fewer than in Sangallo's design. As with the designs of Bramante and Sangallo, the dome is raised from the piers on a drum. The encircling peristyle of Bramante and the arcade of Sangallo are reduced to 16 pairs of Corinthian columns, each of 15 metres (49 ft) high which stand proud of the building, connected by an arch. Visually they appear to buttress each of the ribs, but structurally they are probably quite redundant. The reason for this is that the dome is ovoid in shape, rising steeply as does the dome of Florence Cathedral, and therefore exerting less outward thrust than does a hemispherical dome, such as that of the Pantheon, which, although it is not buttressed, is countered by the downward thrust of heavy masonry which extends above the circling wall.
The ovoid profile of the dome has been the subject of much speculation and scholarship over the past century. Michelangelo died in 1564, leaving the drum of the dome complete, and Bramante's piers much bulkier than originally designed, each 18 metres (59 ft) across. Following his death, the work continued under his assistant Jacopo Barozzi da Vignola with Giorgio Vasari appointed by Pope Pius V as a watchdog to make sure that Michelangelo's plans were carried out exactly. Despite Vignola's knowledge of Michelangelo's intentions, little happened in this period. In 1585 the energetic Pope Sixtus appointed Giacomo della Porta who was to be assisted by Domenico Fontana. The five-year reign of Sixtus was to see the building advance at a great rate.
Michelangelo left a few drawings, including an early drawing of the dome, and some drawings of details. There were also detailed engravings published in 1569 by Stefan du Pérac who claimed that they were the master's final solution. Michelangelo, like Sangallo before him, also left a large wooden model. Giacomo della Porta subsequently altered this model in several ways, in keeping with changes that he made to the design. Most of these changes were of a cosmetic nature, such as the adding of lion's masks over the swags on the drum in honour of Pope Sixtus and adding a circlet of finials around the spire at the top of the lantern, as proposed by Sangallo. The major change that was made to the model, either by della Porta, or Michelangelo himself before his death, was to raise the outer dome higher above the inner one.
A drawing by Michelangelo indicates that his early intentions were towards an ovoid dome, rather than a hemispherical one. In an engraving in Galasso Alghisi' treatise (1563), the dome may be represented as ovoid, but the perspective is ambiguous. Stefan du Pérac's engraving (1569) shows a hemispherical dome, but this was perhaps an inaccuracy of the engraver. The profile of the wooden model is more ovoid than that of the engravings, but less so than the finished product. It has been suggested that Michelangelo on his death bed reverted to the more pointed shape. However Lees-Milne cites Giacomo della Porta as taking full responsibility for the change and as indicating to Pope Sixtus that Michelangelo was lacking in the scientific understanding of which he himself was capable.
Helen Gardner suggests that Michelangelo made the change to the hemispherical dome of lower profile in order to establish a balance between the dynamic vertical elements of the encircling giant order of pilasters and a more static and reposeful dome. Gardner also comments "The sculpturing of architecture [by Michelangelo]... here extends itself up from the ground through the attic stories and moves on into the drum and dome, the whole building being pulled together into a unity from base to summit."
It is this sense of the building being sculptured, unified and "pulled together" by the encircling band of the deep cornice that led Eneide Mignacca to conclude that the ovoid profile, seen now in the end product, was an essential part of Michelangelo's first (and last) concept. The sculptor/architect has, figuratively speaking, taken all the previous designs in hand and compressed their contours as if the building were a lump of clay. The dome must appear to thrust upwards because of the apparent pressure created by flattening the building's angles and restraining its projections.If this explanation is the correct one, then the profile of the dome is not merely a structural solution, as perceived by Giacomo della Porta; it is part of the integrated design solution that is about visual tension and compression. In one sense, Michelangelo's dome may appear to look backward to the Gothic profile of Florence Cathedral and ignore the Classicism of the Renaissance, but on the other hand, perhaps more than any other building of the 16th century, it prefigures the architecture of the Baroque
Completion
The dome was brought to completion by Giacomo della Porta and Fontana.
Giacomo della Porta and Domenico Fontana brought the dome to completion in 1590, the last year of the reign of Sixtus V. His successor, Gregory XIV, saw Fontana complete the lantern and had an inscription to the honour of Sixtus V placed around its inner opening. The next pope, Clement VIII, had the cross raised into place, an event which took all day, and was accompanied by the ringing of the bells of all the city's churches. In the arms of the cross are set two lead caskets, one containing a fragment of the True Cross and a relic of St. Andrew and the other containing medallions of the Holy Lamb.
In the mid 18th century, cracks appeared in the dome, so four iron chains were installed between the two shells to bind it, like the rings that keep a barrel from bursting. As many as ten chains have been installed at various times, the earliest possibly planned by Michelangelo himself as a precaution, as Brunelleschi did at Florence Cathedral.
Changes of plan
On 18 February 1606, under Pope Paul V, the dismantling of the remaining parts of the Constantinian basilica began. The marble cross that had been set at the top of the pediment by Pope Sylvester and Constantine the Great was lowered to the ground. The timbers were salvaged for the roof of the Borghese Palace and two rare black marble columns, the largest of their kind, were carefully stored and later used in the narthex. The tombs of various popes were opened, treasures removed and plans made for reinterment in the new basilica.
The Pope had appointed Carlo Maderno in 1602. He was a nephew of Domenico Fontana and had demonstrated himself as a dynamic architect. Maderno's idea was to ring Michelangelo's building with chapels, but the Pope was hesitant about deviating from the master's plan, even though he had been dead for forty years. The Fabbrica or building committee, a group drawn from various nationalities and generally despised by the Curia who viewed the basilica as belonging to Rome rather than Christendom, were in a quandary as to how the building should proceed. One of the matters that influenced their thinking was the Counter-Reformation which increasingly associated a Greek Cross plan with paganism and saw the Latin Cross as truly symbolic of Christianity.
Another influence on the thinking of both the Fabbrica and the Curia was a certain guilt at the demolition of the ancient building. The ground on which it and its various associated chapels, vestries and sacristies had stood for so long was hallowed. The only solution was to build a nave that encompassed the whole space. In 1607 a committee of ten architects was called together, and a decision was made to extend Michelangelo's building into a nave. Maderno's plans for both the nave and the façade were accepted. The building began on 7 May 1607, and proceeded at a great rate, with an army of 700 labourers being employed. The following year, the façade was begun, in December 1614 the final touches were added to the stucco decoration of the vault and early in 1615 the partition wall between the two sections was pulled down. All the rubble was carted away, and the nave was ready for use by Palm Sunday.
Maderno's façade
The façade designed by Maderno, is 114.69 metres (376.3 ft) wide and 45.55 metres (149.4 ft) high and is built of travertine stone, with a giant order of Corinthian columns and a central pediment rising in front of a tall attic surmounted by thirteen statues: Christ flanked by eleven of the Apostles (except Peter, whose statue is left of the stairs) and John the Baptist.
The façade is often cited as the least satisfactory part of the design of St. Peter's. The reasons for this, according to James Lees-Milne, are that it was not given enough consideration by the Pope and committee because of the desire to get the building completed quickly, coupled with the fact that Maderno was hesitant to deviate from the pattern set by Michelangelo at the other end of the building. Lees-Milne describes the problems of the façade as being too broad for its height, too cramped in its details and too heavy in the attic storey. The breadth is caused by modifying the plan to have towers on either side. These towers were never executed above the line of the façade because it was discovered that the ground was not sufficiently stable to bear the weight. One effect of the façade and lengthened nave is to screen the view of the dome, so that the building, from the front, has no vertical feature, except from a distance.
Maderno's nave
To the single bay of Michelangelo's Greek Cross, Maderno added a further three bays. He made the dimensions slightly different from Michelangelo's bay, thus defining where the two architectural works meet. Maderno also tilted the axis of the nave slightly. This was not by accident, as suggested by his critics. An ancient Egyptian obelisk had been erected in the square outside, but had not been quite aligned with Michelangelo's building, so Maderno compensated, in order that it should, at least, align with the Basilica's façade.
The nave has huge paired pilasters, in keeping with Michelangelo's work. The size of the interior is so "stupendously large" that it is hard to get a sense of scale within the building. The four cherubs who flutter against the first piers of the nave, carrying between them two holy water basins, appear of quite normal cherubic size, until approached. Then it becomes apparent that each one is over 2 metres high and that real children cannot reach the basins unless they scramble up the marble draperies. The aisles each have two smaller chapels and a larger rectangular chapel, the Chapel of the Sacrament and the Choir Chapel. These are lavishly decorated with marble, stucco, gilt, sculpture and mosaic. Remarkably, there are very few paintings, although some, such as Raphael's "Sistine Madonna" have been reproduced in mosaic. The most precious painting is a small icon of the Madonna, removed from the old basilica.
Maderno's last work at St. Peter's was to design a crypt-like space or "Confessio" under the dome, where the cardinals and other privileged persons could descend in order to be nearer to the burial place of the apostle. Its marble steps are remnants of the old basilica and around its balustrade are 95 bronze lamps.
St. Peter's Piazza
To the east of the basilica is the Piazza di San Pietro, (St. Peter's Square). The present arrangement, constructed between 1656 and 1667, is the Baroque inspiration of Bernini who inherited a location already occupied by an Egyptian obelisk which was centrally placed, (with some contrivance) to Maderno's façade. The obelisk, known as "The Witness", at 25.5 metres (84 ft) and a total height, including base and the cross on top, of 40 metres (130 ft), is the second largest standing obelisk, and the only one to remain standing since its removal from Egypt and re-erection at the Circus of Nero in 37 AD, where it is thought to have stood witness to the crucifixion of St Peter. Its removal to its present location by order of Pope Sixtus V and engineered by Domenico Fontana on 28 September 1586, was an operation fraught with difficulties and nearly ending in disaster when the ropes holding the obelisk began to smoke from the friction. Fortunately this problem was noticed by Benedetto Bresca, a sailor of Sanremo, and for his swift intervention, his town was granted the privilege of providing the palms that are used at the basilica each Palm Sunday.
The other object in the old square with which Bernini had to contend was a large fountain designed by Maderno in 1613 and set to one side of the obelisk, making a line parallel with the façade. Bernini's plan uses this horizontal axis as a major feature of his unique, spatially dynamic and highly symbolic design. The most obvious solutions were either a rectangular piazza of vast proportions so that the obelisk stood centrally and the fountain (and a matching companion) could be included, or a trapezoid piazza which fanned out from the façade of the basilica like that in front of the Palazzo Pubblico in Siena. The problems of the square plan are that the necessary width to include the fountain would entail the demolition of numerous buildings, including some of the Vatican, and would minimise the effect of the façade. The trapezoid plan, on the other hand, would maximise the apparent width of the façade, which was already perceived as a fault of the design.
Bernini's ingenious solution was to create a piazza in two sections. That part which is nearest the basilica is trapezoid, but rather than fanning out from the façade, it narrows. This gives the effect of countering the visual perspective. It means that from the second part of the piazza, the building looks nearer than it is, the breadth of the façade is minimized and its height appears greater in proportion to its width. The second section of the piazza is a huge elliptical circus which gently slopes downwards to the obelisk at its centre. The two distinct areas are framed by a colonnade formed by doubled pairs of columns supporting an entabulature of the simple Tuscan Order.
The part of the colonnade that is around the ellipse does not entirely encircle it, but reaches out in two arcs, symbolic of the arms of "the Catholic Church reaching out to welcome its communicants". The obelisk and Maderno's fountain mark the widest axis of the ellipse. Bernini balanced the scheme with another fountain in 1675. The approach to the square used to be through a jumble of old buildings, which added an element of surprise to the vista that opened up upon passing through the colonnade. Nowadays a long wide street, the Via della Conciliazione, built by Mussolini after the conclusion of the Lateran Treaties, leads from the River Tiber to the piazza and gives distant views of St. Peter's as the visitor approaches.
Bernini's transformation of the site is entirely Baroque in concept. Where Bramante and Michelangelo conceived a building that stood in "self-sufficient isolation", Bernini made the whole complex "expansively relate to its environment".