The Basilica of Saint Peter (Latin: Basilica Sancti Petri), officially known in Italian as the Basilica di San Pietro in Vaticano and commonly known as St. Peter's Basilica, is located within the Vatican City. St. Peter's has the largest interior of any Christian church in the world, holding 60,000 people. It is regarded as one of the holiest Christian sites and has been described as "holding a unique position in the Christian world" and as "the greatest of all churches of Christendom".While St. Peter's is the most famous of Rome's many churches, it is not the first in rank, an honour held by the Pope's cathedral church, the Basilica of St. John Lateran.
Catholic tradition holds that Saint Peter's tomb is below the altar of the basilica. For this reason, many Popes, starting with the first ones, have been buried there. There has been a church on this site since the 4th century. Construction on the present basilica, over the old Constantinian basilica, began on April 18, 1506 and was completed on November 18, 1626.