During the great persecution against the Christians of Nerone in 64 AD, which had as its backdrop the circus of Caligula, St. Peter also suffered martyrdom, crucified and deposed, as we read in Liber Pontificalis (I, 118): “via Aurelia […] iuxta palatium Neronianum, in Vaticanum” (in the Vatican, on the Via Aurelia in front of Nerone’s palace). Among the testimonies that identify the place of martyrdom, a passage by Eusebius from Caesarea (4th century) quotes a letter written by Gaius to Proclus in which the presbyter invites his friend to come to Rome: “to the Vatican and on Via Ostiense, you you will find the trophies of those who founded this Church.” Precisely because of the importance of this testimony, the 2nd century aedicula, found during excavations in the Vatican Necropolis to protect the burial of St. Peter, has been called the “Trophy of Gaius”.
Following the proclamation by the emperor Constantine of the Edict of Milan (313 AD), the Christians had the faculty to build their buildings of worship: it was Constantine who started the construction of the Basilica in 324 which was to incorporate the ” Trophy of Gaius “and make the tomb of Peter the fulcrum of the structure. Consecrated in 329, the great Basilica was presented as a longitudinal plan building with five naves and a transept. Outside, a staircase led to the quadriportico in front of the Basilica, also known as Paradiso, at the center of which there was a fountain for the ablutions of the catechumens identified with the large bronze pine cone, also remembered by Dante in the Divine Comedy (“his face me it looked long and thick / like the pina of San Pietro in Rome “Inf. XXXI 58-60) and now located in the homonymous courtyard of the Vatican Museums.
It was in this Basilica that, on Christmas Eve in the year 800, Charlemagne, king of the Franks, was crowned emperor of the Holy Roman Empire; it was in this Basilica that until the beginning of the 1300s masses of pilgrims from all over Europe flocked to venerate the tomb of the “Prince of the Apostles”.
With the abandonment of Rome during the Avignon schism (1309-1377), the basilica, which was already more than a thousand years old, began to have increasing static and conservation problems. There is not much news on the subject, but it is certain that Pope Nicholas V in the mid-1400s had the architect Bernardo Rossellino draft a project that included a new choir, outside the Constantinian apse: it was partially built for a height of about one and a half meters.
At the beginning of the 1500s the choice whether to restore or completely rebuild St Peter was ever more pressing, so much so that the new Pope Julius II, elected in October 1503, decided in 1505 to entrust the task to Donato Bramante, one of the greatest architects of the time, who was already in Rome: he will be nicknamed “Maestro Ruinante” for this undertaking. Many of his drawings are kept in the Uffizi in Florence. All of them, however, have one thing in common: that of proposing a square plan inside which a Greek cross with four protruding apses is inserted; the square that becomes a cube in space is covered in the center by a hemispherical dome. As has been observed (A. Bruschi, 1984), the whole is inspired by a precise symbolism, “schematized – according to an ancient tradition especially in the Byzantine environment – in a cube (the earth) expanded into four arms (the four parts of the world) and surmounted by a dome (the sky) “.
On April 18, 1506, a great ceremony was started for the construction of the first pylon; the following year the foundations of the other three support structures were laid. But the deaths of Julius II (1513) and Bramante (1514) stopped the construction that had reached the top of the four pillars.
Other projects were elaborated during the following 40 years, animatedly debating whether the new St Peter should have a central plan, dear not only to Bramante but in general to all the architects of the Renaissance, or longitudinal and therefore a Latin cross, more responsive to the ecclesiastical tradition and at the same time more suitable to cover the whole sacred area of the ancient Constantinian Basilica. With the constraint of the four central pylons now built, Raffaello (1514) and Antonio da Sangallo the Younger (1538) proposed a longitudinal plan, Baldassarre Peruzzi (1520) a central plan.
Finally in 1547 Michelangelo was commissioned by Pope Paul III to draw up a new project. He returned to the central Bramante plant, however making both the pillars and the perimeter wall thicker, and also digging the masonry to obtain niches and protrusions. His project included a large dome that was to cover the central area, where the papal altar was also located. The construction was finally completed, with the exception of the dome, and after the Maestro’s death in 1564, his pupil Giacomo Della Porta had to carry out the great feat, not without some modifications such as raising the curvature of the cap.
The dilemma of the choice between central and longitudinal plan was not yet definitively resolved. The Council of Trent, which ended in 1563, recommended the use of the longitudinal structure in churches. For this reason, the architect Carlo Maderno was commissioned to extend what Michelangelo had already done: he did so by adding two spans and thus transforming San Pietro into a church with a Latin cross plan. And Maderno was also the author of the “classic” facade, built from 1607 to 1612: however, it had the defect of hiding and visually removing Michelangelo’s dome. The Bernini square in front will be all aimed at giving a solution to the problem of bringing the large structure closer to the observer.