This is a 13th-century church whose construction began around 1220. It took nearly 60 years to complete the project. The abbey was supported by the Republic of Siena for nearly 100 years but was ransacked by mercenaries in 1363. In 1786 the bell tower fell in, taking with it the roof of the church. Despite being in ruins, the shell of the church is magnificent to behold and is situated among a beautiful forest.