On Bramante‘s death in 1514 Raphael was entrusted with the direction of the new St. Peter’s basilica believing that he would be the one who could most faithfully develop such a project. Like Bramante, Raphael also came from Urbino and his career in the Pontifical Court, according to Vasari, had begun under the protection of the great architect. Raphael’s design changed the Basilica’s floor plan and wanted to include a wide nave of five bays, with a row of complex apsidal chapels off the aisles on either side. But Raphael wasn’t the most suitable genius for such a gigantic construction, and although the great Florentine architect Antonio da Sangallo assisted him, the works on St. Peter’s didn’t progress much. Finally, after Raphael died in 1520, his successor in the works of the Basilica was Baldassare Peruzzi, who kept the changes that Raphael had proposed to the internal arrangement of the three main apses, but reverted to the Greek Cross plan and other features designed by Bramante. Peruzzi’s plan did not go ahead because of various difficulties. In 1527 Rome was sacked and plundered, and Peruzzi died in 1536 without his plans for the Basilica being realized.
Raphael’s assistant, Antonio da Sangallo the Younger, proposed a plan which combined features of Peruzzi, Raphael and Bramante’s design. Sangallo’s main practical contribution to the works was to strengthen Bramante’s piers which had begun to crack. However, Sangallo died in 1546 and no one seemed capable of bringing the construction to fruition but Michelangelo, then in his seventies, his reputation growing more and more every day. On 1 January 1547 under the reign of Pope Paul III, Michelangelo succeeded Sangallo the Younger as the Capomaestro, the superintendent of the building program at St Peter’s. “After Antonio da Sangallo died in 1546,” says Vasari, “and as there was no one who directed the factory of Saint Peter, there were different opinions, until His Holiness, inspired by God, decided to entrust it to Michelangelo, who refused saying, to excuse himself from that burden, that his art wasn’t that of architecture. Finally, not admitting his scruples, the Pope ordered him to accept it, and so much against his will, he had to be in charge of that endeavor…”
Michelangelo suppressed countless details of Sangallo’s last project, numerous towers, spires and colonnades from the outside, which took away St. Peter’s original classical simplicity, but which, being a reason for considerable expenses, seemed to please the administrators of the architectural works and aroused the animosity of those who saw benefits in delaying the Basilica’s construction that so far had been lasted nearly half a century. To dispel all suspicion of sordidness, Michelangelo demanded that in the motu proprio (an edict personally issued by the Pope) in which he was appointed director of the works with full authority to do and undo, add and remove, it should be noted that he served the Church without any reward (monetary) and just for the love of God. Pope Paul III, who saw in the glorious sculptor the genius appropriate to finish the work, always supported Michelangelo against the intrigues of his enemies. “Your task”- said the sculptor to the administrators in the year 1551 – “is to make sure that the alms arrive and to see that they are not taken away by thieves; the plan and drawings of the church, on the other hand, are my sole responsibility.”
Michelangelo’s intervention in Saint Peter’s project consisted mainly in simplifying the floor plan, that is, to return to Bramante’s general idea, removing accessory elements that weakened the construction, as well as porticoes and openings that reduced the walls’ resistance. Instead, Michelangelo raised the dome to a much higher height than intended. Bramante had wanted to rebuild the Roman dome of the Pantheon, grandiose on the inside, but without a particular visual appealing on the outside. Michelangelo replaced it with a dome like that of Santa Maria del Fiore in Florence, and thus what he took away from the Basilica in extension, he gave it in height. Undoubtedly, what characterizes the exterior of the church of St. Peter in Rome today is its dome with its colossal height of 131 meters dominating the entire building.
Michelangelo redesigned St. Peter’s dome in 1547. Similar to the dome of Florence’s cathedral, St. Peter’s dome is built of two shells of brick, the outer one having 16 stone ribs, twice the number at Florence. Michelangelo’s dome is raised from the Basilica’s huge Bramante’s piers on a drum and is in the exterior encircled by a peristyle of 16 pairs of Corinthian columns, each of 15 meters (49 ft) high and connected by an arch. Also, taking from the design of Santa Maria del Fiore, St. Peter’s dome is ovoid in shape, rising steeply and therefore exerting less outward thrust than a hemispherical dome does (like that of the Pantheon).
Michelangelo died in 1564, when only the base of the cupola had been built, but he left a detailed wooden model still preserved. The work on the dome continued under Michelangelo’s assistant Jacopo Barozzi da Vignola with Giorgio Vasari appointed by Pope Pius V as a supervisor to make sure that Michelangelo’s plans were carried out exactly. Despite all, the construction advanced little during this period. In 1585 the energetic Pope Sixtus V appointed Giacomo della Porta (assisted by Domenico Fontana), as Michelangelo’s successor in the direction of the works. Giacomo, in fact, was Michelangelo’s favorite disciple. Most of the changes della Porta considered on Michelangelo’s design for the dome were of a cosmetic nature, such as the addition of lion’s masks over the swags on the drum in honor of Pope Sixtus and adding a circlet of finials around the spire at the top of the lantern, as previously proposed by Sangallo. He also gracefully altered the design of the upper lantern, making it richer and more complicated, almost baroque in appearance. This slightly more modern detail placed on top of the curved gray surface of the dome covered with sheets of lead, completed the beauty of this magnificent work.
Giacomo della Porta and Domenico Fontana finally completed the dome in 1590, the last year of the pontificate of Sixtus V. His successor, Gregory XIV, oversaw Fontana complete the lantern and had an inscription to the honor of Sixtus V placed around the dome’s inner opening. The next pope, Clement VIII, had the cross placed on top of the lantern, an event that 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 for relics, one containing a fragment of the True Cross and a relic of St. Andrew and the other containing medallions of the Holy Lamb. Around the dome, in the inside, is written in letters 1.4 meters (4.6 ft) high: TV ES PETRVS ET SVPER HANC PETRAM AEDIFICABO ECCLESIAM MEAM. TIBI DABO CLAVES REGNI CAELORVM (“… you are Peter, and upon this rock I will build my church. I will give you the keys of the kingdom of heaven” following Matthew 16:18–19). Also, Beneath the lantern is the inscription: S. PETRI GLORIAE SIXTVS PP. V. A. M. D. XC. PONTIF. V. (To the glory of St Peter; Sixtus V, pope, in the year 1590, the fifth of his pontificate).
Seen from afar, the dome of St. Peter’s Basilica stands out from the slightly uneven plain of Lazio, and it is what characterizes Rome’s landscape the most. As Rome is located to one side of the Vatican, the sun always sets behind the dome cutting out its silhouette against the dusk. For centuries, hundreds of Romans gather every evening on the terraces of the Pincian gardens, on the other side of the Tiber in front of the Vatican, to witness this superb spectacle offered by the conjunction of nature and human ingenious.
St. Peter’s dome is, truly, a moral entity endowed with its own spirit, so similar and yet so different from Florence’s dome and from all those other domes that were built later in its imitation.
Such was the influence that St. Peter’s dome had on artists that, from the middle of the 16th century onwards, there is no church, no matter how large or small, that doesn’t want to have its own dome as a testimony of admiration for that of Saint Peter in Rome. Not only in Italy, but in all the other countries where the Renaissance arrived, both in rural brick churches covered with stucco or in great monuments such as the Basilica of San Lorenzo de El Escorial in Spain and later in that of the Invalides in Paris, the same motif is always repeated: a church with a cross plan crowned with a dome on a cylindrical drum above the transept. Though Michelangelo’s dome drew heavily from the Gothic profile of the dome of Florence’s Cathedral almost ignoring the Classicism of the Renaissance, it prefigured the architecture of the Baroque perhaps more than any other building of the 16th century.
In addition to the dome it can be said that, with the exception of the façade, the entire exterior of St. Peter’s Basilica was Michelangelo’s work; the church projected by Bramante would have been completely different, with its multiple porticoes and open galleries. It is in the apse of St. Peter’s that Michelangelo’s own style as an architect is understood. The very high curved walls of the apses end in a very simple horizontal attic that runs around the entire temple, apparently supported by colossal Corinthian pilasters. In the smooth spaces, balconies and windows open up showing off their civil and secular designs, but so grandiose that give back the building its religious character that would have been lost if we just consider those openings almost domestic in appearance. Michelangelo’s work in St. Peter’s is generally obscured behind the baroque impression given by the square and the façade, both built much later; but when going around the Basilica, when seeing the huge church with its severe architecture of its walls, and when looking up to the very high cornice seeing those stone canvases unique in the world for its size and nobility, the viewer once again feels the same effect of religious emotion produced by the cathedrals of the Middle Ages. Once again Michelangelo managed, with his elevated artistic and personal spirit, to give a new mystical meaning to the lavish work originally intended to carry out by the mundane ambitions of the Rome of the Renaissance.