The tomb and mortal remains of the pope St. Leo the Great.
Above the altar where he is buried, there is a majestic, high-relief marble portrait of Leo the Great as he met Attila the Hun, the scourge of god, near Mantua. The Pope's words were convincing, Attila was persuaded not to attack Rome. He told his troops that when the Pope spoke he saw the threatening figures of Peter and Paul with drawn swords before him. The sculpture was done by Alessandro Algradi (1595-1654) and is the only high relief of this type in the Basilica.