Pilgrims and art lovers flock to this basilica for two reasons: to see St Peter’s chains and to see Michelangelo’s tomb of Pope Julius II. The church was built in the 5th century to house the chains that bound St Peter when he was imprisoned in the Carcere Mamertino. Some time after St Peter’s death, the chains were sent to Constantinople for a period before returning to Rome as relics. They arrived in two pieces and legend has it that when they were reunited they miraculously joined together. They are now displayed under the altar.