The Basilica of Constantine bore the traces of decay and ruin, and the many restorations could not guarantee its preservation. The idea of completely rebuilding it occurred first to Nicholas V (1447-1455), inspired by the ambitious plans of L. B. Alberti, who dreamed of remodeling the face of the entire city. According to Vasari, he became friendly with Nicholas V, who was accustomed to consult Bernardo Rosselino on matters of art. Taking advantage of the favourable disposition of the humanist Pope and of his wish to redesign and repopulate Rome, Alberti prepared a great scheme of reconstruction. He was probably associated with the enormous (and now totally lost) project described by Giannetto Manetti, in which the Tomb of the Apostle was to become the center of the new city. Rossellino, on the other hand, wanted to give the Vatican the aspect of an isolated fortress. The death of Nicholas V stopped all projects, and the work begun by Rosselino in the area of the Porta Angelica was limited to the Torrione, the north wing of the buildings around the Cortile del Pappagallo, and the most urgent restorations in the Basilica, especially around the Tomb of the Apostle.
Alberti, although he had great respect for the ancient buildings, had decided upon his radical plan after noticing that the southern wall of the old Basilica was almost six feet out of line, and that the northern wall was leaning towards the interior and causing strain on the roof. We know from Grimaldi that the paintings in the nave were almost invisible because of the inclination of the wall and the dust that had accumulated on it; while in his judgment all the painting done under Pope Formosus appeared "quite poorly executed, barbaric, and over-elaborate." Neither Calixtus III, occupied as he was with the serious threat of the Turks, nor Pius II, who built the Loggia delle Benedizioni and restored the roof the Basilica, nor the great collector Paul II, the creator of the Palazzo Venezia, nor Sixtus IV, to whom we owe the Sistine Chapel (as Pollaiolo's sepulchral monument of 1493 justly reminds us), dared to face the dilemma of either restoring the Basilica from the ground up, or of demolishing it.
All hesitation ceased with the accession of Julius II. The impetuous Pope, encouraged by the presence of the great architects who were renewing the architecture of Italy and of Rome according to the norms of Renaissance culture, and inspired by the fervour of renewal brought about by the new Humanism, ordered Donato Bramante to prepare the plans which we now know only through a drawing of Antonio Sangallo and a medal of Caradosso. These plans were in accordance with the classical ideal of an architecture of pure space: the focus of attention in the center, with a hemispherical cupola, surrounded by four minor cupolas, at the point of intersection of the arms of a Greek cross (a scheme not very different from what we see in the central nucleus of the present edifice). On the Saturday in Albis, i.e., 27 April 1506, Julius II descended to the foundations of the great pillar of Saint Veronica and, surrounded by a crowd of cardinals and the first groups of skilled workers, laid the first stone. He wished to celebrate with a solemn ceremony the "renewal" of the Vatican, which was "run down from old age and neglect (vetustate et situ squalentem)" De Conti, an eyewitness to the events of the papal court during those years, states that "the designs for the work promise to surpass in beauty and proportion every monument of antiquity. Above the Basilica will arise a vaulted roof more spacious and higher than the Pantheon". Bramante quickly modified the arches of the four great pilasters and demolished the external walls.
At Bramante's death, (11 March 1514), a triumvirate of architects was formed, composed of Giuliano Sangallo, Raphael and Fra Giocondo da Verona. They formulated a new plan, whose design can be seen in the fresco on the wall of the Sala dei Chiaroscuri in the Vatican Museum. The new project radically altered the conception of Bramante by elongating the nave. This triumvirate of geniuses was dissolved in 1520 by the death of both Raphael and Fra Giocondo. They were replaced by Antonio Sangallo and Baldassare Peruzzi, who decided to undo a great part of what had already been accomplished. The Sack of Rome in 1527, with its tragic consequences, slowed down even further the construction, which had not been progressing quickly even before.
When Peruzzi died in 1536 (it is difficult to assess his contribution to the work), Antonio Sangallo assumed the supervision of the building. It took the forceful intervention of Paul III, however, to get him to finish the one-in-thirty wooden scale model (still to be seen in the Basilica, in the octagon of Saint Gregory). At the end of 1539 the laying of the foundation for the apse was begun, along with the destruction of all that remained of the old Basilica except the transept.
The floor level of the Basilica was raised about ten feet by Sangallo (the precise reason is unknown). Some guess that the motive was to give a more firm underpinning to the new church. Eventually the space between the floor of Constantine's Basilica and that of Sangallo's became the Vatican Grotto - but not until the pontificate of Gregory XII.
In 1538 a dividing wall was erected between the eleventh and twelfth columns of the nave to allow the canons to perform services and visitors to enter. From drawings of the period we can deduce that the lower order of Sangallo's external walls was standing; while by 1546 the four great vaults of the cross were already completed.
When, after repeated requests, Michelangelo resigned himself to taking over the supervision of the works, "without pay and without reward", as the Brief of Paul III states, he requested and obtained from the Pope a free hand in everything. Returning to Bramante's idea of a centrally focused building, he undid all the work of Sangallo, beginning with the immense external walls and the support of the four pilasters.
His most pressing preoccupation was to get the construction finished to a point where further modifications would be impossible. With this in mind, he constructed the first order of the left arm of the cross-vault and the external hemisphere facing southeast, and finished the internal and external cupolas as far as the drum.
In knocking down the external construction of Sangallo, he shortened the perimeter of the apse or tribune by about 36 feet ("he reduced Saint Peter's in size, and increased it in grandeur", says Vasari), and reduced the number of chapels in the hemisphere from eight to three. The vault arm to the right of the tribune was finished in December 1547; the large vault in August 1549; the cornice of the cupola drum in December 1550.
In December 1552 the external line and the internal pairs of pilasters of the drum were completed; in November 1553 the large vault was "closed". Between 1551 and 1557 Michelangelo worked on the model of the "keep"; in 1556 he finished the reinforcement of the pillars which were to support its great weight; in May of 1558 the keystone of the Cappella del Re was placed in position.
It was a memorable event, celebrated with great solemnity. With the closing of the vault of the Cappella del Re, Michelangelo could claim that he had completed the essential part of his gigantic project, despite the complications of circumstances, the rivalries and jealousy of his enemies, and the technical and financial difficulties.
After a period of near inertia caused by the lack of funds, which had ceased arriving especially from Spain, in November 1558 Michelangelo started making his wooden model of the cupola, and finished it in December 1561. Work continued feverishly on the vaults of the great arches and on the base of the drum, and the ailing Michelangelo had himself carried to the spot to be close to the work and to follow the growth of his difficult but most beloved creation.
But what difficulties and what calumnies there were! He had requested and obtained from Pope Julius III, in 1552, a renewal of the rescript of Pope Paul, reinforced with the threat of interdict against anyone who should dare "to reform or change in the least, at any time or in any way, the model and design made by you".
In 1562 and the years following, work proceeded on the raising of the columns, the upper courses of the pillars, and the capitals of the drum. We have no certain information on the completion of the Attic order, which looks quite different in prints of the 1500's (e.g. that of V. Luchino from 1564) from the present structure. In any case, with the impost of Marchion di Pietro put into place and attached on 24 May 1564, the drum could be said to be finished. Michelangelo had died several months before, on the 18 February, at his home at Macel de' Corvi, near Trajan's Forum. He was sure that no one could now spoil his Saint Peter's and that he had brought into being the most important monument of sacred architecture of all time, giving glory to God and averting "a great shame for Christianity".
During the brief pontificate of Pius IV the two architects of the Basilica, Pirro Ligorio and Giacomo Barozzi (Vignola),did no more than complete the interior decoration of the apse and transept and draw up plans (subsequently abandoned) for the cupola of the chapel of Saint Gregory.
Vasari claims the credit for persuading Pius V not to abandon Michelangelo's ideas; it would therefore not be rash to suspect that the removal of Ligorio was due precisely to this. In fact, when the Pope named Vignola chief architect in 1567, he imposed on him, in accordance with the rescript of Julius III, the obligation of following Michelangelo's plan and of not changing anything. Vignola was known to Pius V through his having prepared the hall of the Conclave from which the latter emerged as Pope, and for having drawn up the plans of the church of the Gesu.
The diagram of Lafrery from 1577 and the drawing by an unknown artist of 1580 show precisely the situation of the Basilica in those years prior to Sixtus V's intervention. Even though, he was concerned with a campaign against the Turks, and had admonished the cardinals to "edify the world less by their buildings and more by their virtue", Saint Pius V devoted large sums of money to the construction of the Basilica, and hastened the study of the difficulties which were impeding the vaulting of the cupola. Gregory XIII (Ugo Boncompagni) also continued the construction, if only because he wished to please his countryman, Vignola (who did not in fact achieve any appreciable results, so far as we know).
A great step forward took place, however, with the naming of the Roman Giacomo della Porta as architect. Gregory XIII appointed him at the suggestion of Tommaso de' Cavalieri, the great friend of Michelangelo. A record of the beginning of the payment of a salary of 50 scudi per month to della Porta is found in the Acts of the Archive, under the date 12 May 1574. For Gregory, della Porta first of all studied the completion of the Cappella Gregoriana, and drew a new plan for the cupola to replace that of Vignola; he then eliminated the temporary choir and designed another for the new tribune. The cupola of the Capella Gregoriana was finished in December of 1577. The columns, taken from the temple of Romulus, were installed at the sides of the altar, and the ancient image of Our Lady Help of Christians was exposed for the veneration of the faithful at a solemn ceremony on 12 February 1578. The relics of Saint Gregory Nazianzen, which had been kept up to then in the Campo Marzio, were placed under the altar.
But it is under Sixtus V that della Porta, aided by Domenico Fontana, faced the problem of the great cupola. Already by 1565 there had been agreement on the "great internal and external cornice", a committee had been named specifically to administer the undertaking, and work continued so assiduously in the enormous construction yard that we have a record from June 1584 that "the church of Saint Peter is growing on every side". In reality, however, no one had dared to face the basic problems.
Sixtus V was not the man to tolerate an uncertain position. The Jesuit Friesti recounts that the Pope kept repeating that the church as it stood looked like a body with the head cut off. He consulted with architects, discussed the problems, saved money. Finally, on 15 June 1588, he thought the time had come to begin work. Eight hundred workers, according to Fr Angelo Rocca, an eyewitness (or 600, according to Bonanni and Fontana) worked day and night. Della Porta, despite his poor health, made anxious calculations of the problems of stress and modified - according to some - the curve of the internal and external shells of Michelangelo's model. Fontana and the supervisors did not allow themselves a moment's rest in their work to complete the "construction which will be counted", as Fontana himself says, "as one of the wonders of the world".
Sixtus V, guessing that his days were numbered, pressed everyone to work quickly, with his characteristic remark that there were other important things to be done; and, in fact, we have only to look at the Avvisi di Roma from those years to realize the astounding activity he engaged in and the enormous extent of the projects he undertook. It took only 22 months and about 200,000 gold scudi to complete the awe-inspiring structure to the height of the lantern. This was not an extravagant sun, considering that the Basilica, from the foundation to the drum, had cost more than 500,000 scudi and taken more than half a century of work.
The polemical and triumphal tone of the Avviso of 21 May 1590 indicates the state of mind induced by the progress in construction: "To his own everlasting glory, and to the shame of his predecessors, our Holy Father Pope Sixtus V has completed the vaulting of the cupola". The last stone, inscribed with his name, had been put in place a week earlier, on 14 May. All that was left to be finished was the metal covering on the surface of the cupola, the bronze cladding of the ribs, the columns of the lantern, and the bronze ball and cross; these took seven more months.
14 May was a day of triumph not only for the Pope but also for the aged architect. Baglione recalls with emotion that only a Roman could have understood and brought to completion such a gigantic undertaking.
It is interesting to note that it was just at this time, while the serious problems were being discussed, that the idea occurred of strengthening the curved walls with iron chains. The first application of "armed" cement (technical expression was "to arm the cupola with chains") took place (contrary to the inaccurate writings of Baldinucci, supported by Fontana but rightly contested by Poleni) in April 1589. On 15 April Pietro Paolo Ferraro furnished the first ring of iron, weighing 18,225 pounds; a second and identical one followed the next month; and in August arrived a third and smaller ring of 16, 523 lbs. The ball, weighing 5,493 lbs., and the cross of 850 lbs. were hoisted into position on top of the lantern in 1592 by Niccolo Faccalume and Battista Torrigiani, brass workers of the Borgo.
The decoration of the intrados of the cupola was 1593 onwards in the hands of Giovanni Guerra, Cesare Nebbia, and Marcantonio Bosco, who organized the so-called "exhibitions" to study the effect of their cartoons seen from below.
In the four medallions of the corbels below the cupola, (28 feet in diameter), Giovanni De Vecchi portrayed directly in mosaic Saint John the Evangelist and Saint Luke; Cesare Nebbia of Orvieto designed Saint Mark and Saint Matthew (the pen of the former is almost 9 feet long). The angels and cherubim are by Cristoforo Roncalli and Giuseppe Cesare d'Arpino; there are Popes and Saints also by Giovanni Guerra and Cesare Nebbia; the decorative motifs between the 16 ribs of the vaulting are by Cristoforo Pomarancio. At the plinth of the drum the diameter of the cupola is 139 feet, and in this immense space the artists placed their 96 figures. Marcantonio Bosco painted the architrave, the frieze and the cornices; Ercole da Fano the eye of the lantern. We know that Orazio Gentileschi was also involved in this gigantic series of pictures, but the documents do not specify his contribution.
The cartoons of the painters were transformed into mosaic by a team of artisans: Cesare Torelli, Donato Parigi, Ranuccio Semprevivo and Rosario Parasole. They also executed the mosaic of the lantern. Between 1605 and 1606 Ventura painted the letters of the Tue es Petrus and Piero Pomodoro applied the gold and blue. The letters are over 4.5 feet high. Above them is the ambulatory, 433 feet in circumference. Rocco Solaro modeled in stucco the 14 types of animals chosen to decorate the windows, the so-called "mountains" of the piers of the drum, the candlesticks of the niches, and all the mouldings.
The drum is 65.6 feet high and contains 16 windows with alternating frontispieces between Corinthian pilasters supporting the beams and cornice. At this point one is 240 feet from the ground, and here begins the cupola erected by Sixtus V, who is commemorated by the lions' heads taken from his armorial bearings. From the floor to the arms of the cross, the basilica is 450 feet high.
It was not necessary to await the implementation of the Council of Trent and the decrees of the new Congregation of Rites created by Sixtus V to celebrate with ceremonies, flabella and processions the prestige of the Basilica of Saint Peter.
It is fitting to recall that the external splendour of worship and the sumptuousness of the sacred ornaments ("teatro" was the technical term used to designate the decoration of the Basilica for great functions) have their own history which begins with Johann Burkhart, Clericus Ceremoniarum from 1483 to 1506, continues with Paride de Grassis and Tiberio Alfarano, and on to Amici, Grimaldi, Canori, and Bagnaroli, who followed in the footsteps of the great and irascible German Master of Ceremonies. So great was the importance given to the solemnity of ceremonies that on 22 August 1575 the canons decided to raise the monthly salary of Pier Luigi da Palestrina from 8 to 15 scudi, fearing that the great polyphonist might leave the Cappella Giulia for Santa Maria Maggiore.
The Chapter of Saint Peter's was of the opinion that the Basilica's design of a Greek cross was not really suitable for the complex movements of the innumerable persons taking part in ceremonies, which were particularly picturesque and complicated when the Pope was present.
This, however, was not the official reason for the order to destroy the remaining part of the old Basilica. On 11 October 1605 Cardinal Evangelista Pallotta, the archpriest, arranged for the carrying out of the order given by Paul V on 26 September to proceed with the destruction of the remaining half of the Constantinian building. The reasons were technical: "according to the opinion of the most expert architects, the walls of the central nave were leaning inwards some 3.5 feet from top to bottom and were full of cracks; and the rafters and the roof, already rotten with age, were about to collapse".
The work began immediately. On 2 October the Blessed Sacrament was transferred from the Oratory of Saints Simon and Jude to the Cappella Gregoriana, and the Oratory, built in 1584, was destroyed. The adjacent chapel of the Madonna della Colonna was also pulled down, thus giving access to the Caetani chapel where Boniface IV was buried. Next to it, between the Ravenna and Judgment doors, was the tomb of Boniface VIII, Dante's adversary. As was the custom, when this tomb was opened the corpse was inspected for identification purposes. To everyone's surprise it was found intact, and the Chapter decided to place it on public view until 28 November.
Between the end of 1605 and the end of 1608 the demolition was carried out with dispatch, despite the criticism of old Romans; quod non fecerunt barbari, people started to murmur, fecerunt Barberini, namely Paul V, who was a member of the Barberini family. Eventually all the altars along the central nave were eliminated, then those of the side aisles. The outer walls were pulled down, as well as the offices of the Datary, the school of the Cappella Giulia, the houses around the Cortile della Pigna and the little chapel of the Madonna della Febbre. The house of the canon Pomponio De Magistris, the little Church of Sant' Andrea, and the Oratory of the Blessed Sacrament disappeared in an instant. On 7 May 1607 Cardinal Pallotta was able to bless the first stone of the new foundation, which "was placed in front of the door of the Cappella Gregoriana, where the new sacristy was to rise".
Grimaldi recounts that during the excavations "they found a brick building with vaults painted with flowers and a pilastered portico". The building was immediately buried, as was also the case with another flower-decorated construction found under the atrium of the old Basilica. These were the first excavations under the floor of the Constantinian basilica, and this evidence of the existence of a necropolis in the Vatican area was confirmed by the excavations of 1940.
In November of 1608 the last demolition took place with the pulling down of the Cappella del Coro constructed in 1479 by Guglielmo Rocca, Archbishop of Salerno. At the same time, Tito da Sarzana was working to lay the foundations in the direction of the Tribune, Giorgio Staffetta towards the Camposanto where the chapel of the Madonna della Febbre had stood, and Pietro Drei in the area of the façade, towards the Palace.
At the beginning of 1607 the plans of Carlo Maderno were selected from among those presented in a competition in which Flaminio Ponzio, Domenico Fontana, Girolamo Rainaldi, Ludovico Gigoli and others participated. The much-maligned lengthening of the Basilica - the poor Maderno was judged by Milizia "guilty of lèse architecture" - was reduced to six chapels, which nonetheless irretrievably altered the design of Michelangelo.
It must be admitted that Michelangelo had neglected to include in his plans the Cappella del Coro (when the old one was demolished, Maderno planned the erection of a new Choir in the arm of the Tribune - a project never carried out), the baptismal chapel, the sacristy, the portico, and the balcony for the Pope's blessing. That Maderno favoured Michelangelo's idea is shown by the drawing still found in the Uffizi, with a plan for a Greek cross, and by the fact that he reduced the lengthening to the minimum possible; so much so, in fact, that when in the 1600's Eucharistic devotion increased (in the old Basilica, the Blessed Sacrament was kept, after the demolitions, in the chapel of Saints Simon and Jude), there was thought of using for a Blessed Sacrament chapel the space Maderno had destined for the sacristy, and of constructing a new sacristy with houses for the canons. This in fact took place only at the end of the 1700's.
The carpenter Giuseppe Bianchi, aided by Master Donato, made the wooden model of the extension. What happened to it is unknown. We only know that in 1608 it was located in a space behind the Cappella Gregoriana, and that in 1667 it was in the storeroom with the models "made by Bramante, Michelangelo, Carlo Maderno and others". In August 1609 the old façade was razed to the ground, and Tito da Sarzana himself took charge of the placing of the travertine blocks for the new façade.
Grimaldi was a terrified witness of the last "vandalism" of Paul V's architects, although like Alfarano he had been in favour of the lengthening. Under the date 15 November 1609 he notes despairingly: haec fuit ultima missa in choro et in vetere basilica celebrata.
Vain regrets. On 21 November 1610 thirteen horses drew the first column of African marble into place at the jamb of the great door of the façade, and a deposit was given to the workers for the cipollino columns. In December Bernardino Solari began sculpting the eagle and the festoons on the small doors of the facade, and in the following February Guseppe Bianchi had nearly finished the "arming" of the portico roof. On 16 May 1612 "the last vault of the portico was closed, and amid the explosion of fire-crackers and the ringing of bells the inscription of Paul V appeared on the front".