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Status

St. Peter's Basilica is one of the papal basilicas (previously styled "patriarchal basilicas") and one of the four Major Basilicas of Rome the others (all of which are also Papal Basilicas) being the Basilicas of St. John Lateran, St. Mary Major, and St. Paul outside the Walls. The rank of major basilica confers on St. Peter's Basilica precedence before all minor basilicas worldwide. However, unlike all the other Papal Major Basilicas, it is wholly within the territory, and thus the sovereign jurisdiction, of the Vatican City State, and not that of Italy.

It is the most prominent building in the Vatican City. Its dome is a feature of the skyline of Rome and covers an area of 2.3 hectares (5.7 acres). One of the holiest sites of Christianity and Catholic Tradition, it is traditionally the burial site of its titular, St. Peter, who was the head of the twelve Apostles of Jesus and, according to tradition, the first Bishop of Antioch and later the first Bishop of Rome, rendering him the first Pope. Although the New Testament does not mention St. Peter's martyrdom in Rome, tradition, based on the writings of the Fathers of the Church, holds that his tomb is below the baldachin and the altar of the Basilica in the "Confession". For this reason, many Popes have, from the early years of the Church, been buried near Pope St. Peter in the necropolis beneath the Basilica. Construction of the current basilica, over the old Constantinian basilica, began on 18 April 1506 and finished in 1615. At length, on 18 November 1626 Pope Urban VIII solemnly dedicated the Basilica.

St. Peter's Basilica is neither the Pope's official seat nor first in rank among the Major Basilicas of Rome. This honour is held by the Pope's cathedral, the Archbasilica of St. John Lateran, the mother church of all churches in communion with the Catholic Church. However, St. Peter's is functionally the Pope's principal church, as most Papal liturgies and ceremonies take place there due to its size, proximity to the Papal residence, and location within the Vatican City proper. The " Chair of Saint Peter ", or cathedra, an ancient chair sometimes presumed to have been used by St. Peter himself, but which was a gift from Charles the Bald and used by many popes, symbolizes the continuing line of apostolic succession from St. Peter to the reigning Pope. It occupies an elevated position in the apse of the Basilica, supported symbolically by the Doctors of the Church and enlightened symbolically by the Holy Spirit.

As one of the constituent structures of the historically and architecturally significant Vatican City, St. Peter's Basilica was inscribed as a UNESCO World Heritage Site in 1984 under criteria (i), (ii), (iv), and (vi). With an exterior area of 21,095 square metres (227,060 sq ft), an interior area of 15,160 square metres (163,200 sq ft), St. Peter's Basilica is the largest Christian church building in the world by the two latter metrics and the second largest by the first as of 2016. The top of its dome, at 448.1 feet (136.6 m), also places it as the second tallest building in Rome as of 2016. The dome's soaring height placed it among the tallest buildings of the Old World, and it continues to hold the title of tallest dome in the world. Though the largest dome in the world by diameter at the time of its completion, it no longer holds this distinction.