The 10th Century Church of Saint Bartholomew was built by Otto III and is situated on the small Tiberina Island. It was rebuilt in 1624 after being destroyed in the great flood of 1557. The inside has 14 granite columns and, near the altar, a Byzantine fresco depicting the enthroned Virgin with Jesus. The remains of Saint Bartholomew are contained in an ancient porphyry Roman bath. Two wings were added in the 16th and 17th centuries which housed a Franciscan convent and linked the church to two bridges.