The Papal Basilica of Saint Peterislocated within the Vatican City. Saint Peter's Basilica has the largest of any Christian church in the world. In Roman Catholic tradition, the basilica is the burial site of its namesake Saint Peter, who was one of the twelve apostles of Jesus and, according to tradition, the first Bishop of Rome and therefore first in the line of the papal succession. Construction of the present basilica, over the old Constantinian basilica, began on 18 April 1506 and was completed on 18 November 1626. Photo via Newscom