<P> 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), and a volume of 5,000,000 cubic metres (180,000,000 cu 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 . </P> <P> After the crucifixion of Jesus, it is recorded in the Biblical book of the Acts of the Apostles that one of his twelve disciples, Simon known as Saint Peter, a fisherman from Galilee, took a leadership position among Jesus' followers and was of great importance in the founding of the Christian Church . The name Peter is "Petrus" in Latin and "Petros" in Greek, deriving from "petra" which means "stone" or "rock" in Greek, and is the literal translation of the Aramaic "Kepa", the name given to Simon by Jesus . (John 1: 42, and see Matthew 16: 18) </P> <P> Catholic tradition holds that Peter, after a ministry of thirty - four years, traveled to Rome and met his martyrdom there along with Paul on 13 October, 64 CE during the reign of the Roman Emperor Nero . His execution was one of the many martyrdoms of Christians following the Great Fire of Rome . According to Origen, Peter was crucified head downwards, by his own request because he considered himself unworthy to die in the same manner as Jesus . The crucifixion took place near an ancient Egyptian obelisk in the Circus of Nero . The obelisk now stands in St. Peter's Square and is revered as a "witness" to Peter's death . It is one of several ancient Obelisks of Rome . </P> <P> According to tradition, Peter's remains were buried just outside the Circus, on the Mons Vaticanus across the Via Cornelia from the Circus, less than 150 metres (490 ft) from his place of death . The Via Cornelia was a road which ran east - to - west along the north wall of the Circus on land now covered by the southern portions of the Basilica and St. Peter's Square . A shrine was built on this site some years later . Almost three hundred years later, Old St. Peter's Basilica was constructed over this site . </P>

What is the purpose of st peter's basilica