Constantine built San Paolo to commemorate the martyrdom of the saint in nearby Tre Fontane. Pope John VIII later surrounded it by walls to protect it. It was almost completely destroyed by fire in 1823, after which Leo XII gathered offers from all over the world for its reconstruction. The façade is decorated with mosaics and inside the 4 aisles have 80 granite columns. There’s a frieze with mosaics depicting all the Popes, and 5th Century mosaics on the Triumphal Arch. A 13th Century tabernacle of Arnlfo di Cambio, is on the high altar.
