The Basilica was built in 1238, but greatly altered in 1506. The interior was renovated in neo-Gothic style between 1850 and 1853. The Cappellone del Crosifisso contains a miraculous crucifix. There are also 45 Aragon tombs and frescoes dating from the 14C., attributed to Pietro Cavallini, Giotto's student. The apse of the church overlooks a square decorated with a Baroque obelisk dedicated to Saint Dominic.