St Peter's Basilica

St Peter's Basilica, monument in Rome, the principal shrine of the Roman Catholic Church. It was built as a replacement for the neglected structure erected by Constantine the Great in the early 4th century on the traditional site of the tomb of St Peter. The construction of the church spanned more than a century—it was begun by Pope Julius II in 1506 and finally completed in 1626 under Pope Urban VIII—engaged the talents of some of the finest architects of the Renaissance and Baroque periods, and involved a number of changes in design as the project proceeded. According to the original plan of the great Renaissance architect Donato Bramante, who won the competition for its design, the basilica was to be erected in the form of a Greek cross, with a massive central dome. On Bramante’s death, a number of artists were commissioned to complete it, including Raphael, Fra Giacondo de Verona, and Giuliano da Sangallo, who modified the original plan to a Latin cross with three aisles separated by pillars.

In 1546 Pope Paul III commissioned as chief architect the elderly Michelangelo, who reverted to the Greek cross structure. At the time of his death, the drum for the massive dome, nearly 42 m (138 ft) in internal diameter, was almost complete. Under orders from Pope Paul V, Carlo Maderno took over the design of the church. Following papal preference, he once more exchanged the Greek cross for the Latin cross by extending the nave to the east, thus completing the 187-m-long (615-ft-long) main structure. After further embellishments to the façade, later removed, the basilica was finally dedicated by Urban VIII in 1626.

The interior of St Peter’s is filled with many Renaissance and Baroque masterpieces, the most famous of which is Michelangelo’s sculpture Pietà, now housed behind a glass screen following an attack of vandalism. The dome is imposing, rising high above the supposed site of St Peter’s tomb and with balconies adorned with reliefs depicting the basilica’s major relics. Close by is the bronze statue of St Peter, which is among the most venerated monuments in the basilica. The centrepiece of the church is the baldachin, or altar canopy, over the high altar, by Gianlorenzo Bernini. It is 26 m (85 ft) high and was cast out of bronze pillaged from the roof of the Parthenon in 1633. Bernini’s dramatic gilt and marble Cathedra Petri, or Chair of St Peter, centred by a golden oval window depicting the Holy Spirit as a dove, was completed in 1666 and is found in the apse of the basilica.

St Peter’s was the largest church in Christendom until 1989, when it was exceeded by the newly built basilica in Yamoussoukro, Côte d’Ivoire.