The Abbey of St. Pietro building dates back to the 13th Century and was consecrated in 1254 by Pope Innocent IV, St. Francis, and St. Rufinus. Inside are 3 aisles, and five steps lead to the barrel-vaulted transept under which lies the crypt. There are many Gothic sepulchral monuments of the 14th century and in a chapel is a 14th Century fresco. The exterior has pillars and a cornice which divides the front into three sections with three rose windows.