St. Peter's Basilica s an Italian Renaissance church in Vatican City, the papal enclave within the city of Rome.
Designed principally by Donato Bramante, Michelangelo, Carlo Maderno and Gian Lorenzo Bernini, St. Peter's is the most renowned work of Renaissance architecture and the largest church in the world. While it is neither the mother church of the Catholic Church nor the cathedral of the Diocese of Rome, St. Peter's is regarded as one of the holiest Catholic shrines. It has been described as "holding a unique position in the Christian world" and as "the greatest of all churches of Christendom".
Catholic tradition holds that the Basilica is the burial site of Saint Peter, chief among Jesus's Apostles and also the first Bishop of Rome. Saint Peter's tomb is supposedly directly below the high altar of the Basilica. For this reason, many Popes have been interred at St. Peter's since the Early Christian period, and there has been a church on this site since the time of the Roman emperor Constantine the Great. Construction of the present basilica, which would replace Old St. Peter's Basilica from the 4th century AD, began on 18 April 1506 and was completed on 18 November 1626.
St. Peter's is famous as a place of pilgrimage and for its liturgical functions. The Pope presides at a number of liturgies throughout the year, drawing audiences of 15,000 to over 80,000 people, either within the Basilica or the adjoining St. Peter's Square. St. Peter's has many historical associations, with the Early Christian Church, the Papacy, the Protestant Reformation and Catholic Counter-reformation and numerous artists, especially Michelangelo. As a work of architecture, it is regarded as the greatest building of its age. St. Peter's is one of the four churches in the world that hold the rank of Major Basilica, all four of which are in Rome.