St. Peter’s Basilica

“In the Vatican and in Via Ostiense, you will find the trophies of those who founded this Church.”
[Gaius]

During Nero’s great Christian persecution in 64 A.D., Saint Peter was martyred, crucified and buried in Caligula’s Circus. Eusebius of Caesarea (4th century) quotes a letter written by Gaius to Proclus, in which the presbyter invites his friend to Rome, claiming, “in the Vatican and in Via Ostiense, you will find the trophies of those who founded this Church.”

For this reason, the 2nd century aedicule which was intended to protect Saint Peter’s shrine, and which was discovered during the excavations in the Vatican necropolis, was called “Gaius’s Trophy”. After Constantine’s Edict of Milan (313 A.D.) Christians were allowed to construct places of worship. Constantine himself authorized the building of the basilica in 324. It was intended to enclose “Gaius’s Trophy” and to allow Peter’s tomb to become the centre of the structure.

Consecrated in 329, the Great Basilica appeared as a longitudinal building with a nave, four aisles and a transept. Outside, a staircase led to the four-sided portico in front of the basilica, known also as Paradise, with a fountain in the middle for the ablutions of the catechumens. Charlemagne, king of the Franks, was crowned emperor of the Holy Roman Empire in this basilica on Christmas eve in the year 800.

When the Popes abandoned Rome during the Avignon schism (1309-1377), the basilica, which was one thousand years old by then, was showing signs of wear and deterioration.
By the early 16th century, the need to choose between restoring St Peter’s or rebuilding it completely was unavoidable, so much so that the new Pope Julius II, elected in October 1503, decided to entrust this task to Donato Bramante in 1505, one of the greatest architects of his time.

Bramante’s drawing

The square forms a cubical space and is covered in the centre by a hemispheric dome. Work on the first pylon began with great ceremony on 18th April 1506, and foundations for the other three pylons were laid the following year. Construction halted, however, when Julius II (1513) and Bramante (1514) died; by then the basilica had reached the top of the four pylons.

Several other proposals for St. Peter’s were drawn up over the next 40 years, in the midst of heated debate over whether the new St. Peter’s should have a central or longitudinal plan. Bramante and other Renaissance architects preferred the central plan, but the longitudinal plan or Latin cross conformed more to ecclesiastic tradition and would also cover the entire area of the ancient Constantinian basilica. As the four central pylons had already been built, Raphael (1514) and Antonio da Sangallo the Younger (1538) proposed a longitudinal plan, while Baldassarre Peruzzi (1520) favored a central plan.

Finally in 1547, Pope Paul III commissioned Michaelangelo to propose a new design. His solution was to keep Bramante’s original plan, thickening the pilasters and the external walls and creating niches and ledges by chiselling out the walls.

A vast dome was to cover the central area, where the papal altar was to be placed. The building was finished, although the dome was not completed at Michelangelo’s death in 1564. His pupil, Giacomo della Porta, finished building it with a few changes, such as raising the curve of the calotte. The dilemma over choosing between a central or a longitudinal plan was not yet definitely resolved, however. The Council of Trent, which ended in 1563, expressed a preference for longitudinal churches. Carlo Maderno was therefore asked to extend Michelangelo’s original plan.

He achieved this by adding two bays, turning St Peter’s floor plan into a Latin cross. Maderno also designed St Peter’s “classical” façade, built between 1607 and 1612. Unfortunately it tended to hide Michelangelo’s dome and reduce its visual impact. Bernini’s square sought to resolve the problem with an optical effect that draws the dome forward.