Straight up Via Leone Pierleone from Piazza Torre dell'Olio is the pink- and white-banded 13th-century San Domenico. The first altar on the right preserves an early-15th-century fresco of the Triumph of St. Thomas Aquinas, with tiny monks, prelates, and scholars discussing the theologian's writings. There are more 15th-century frescoes in the presbytery and transept chapels, plus a painted crucifix from the 1300s above the main altar. The Cappella Benedetti di Montevecchio in the left transept is said to conserve not just any nail from the True Cross but one that pierced the Lord's hands. On the left wall is a moving 14th-century fresco of the Pietà.