The "Abbey of San Galgano" was erected from about 1220 on, near the place, where San Galgano once had lived in a hermitage. Legends tell, that San Galgano had visions. In one vision he arrived accompanied by archangel Michael on top of the Monte Siepi, where he met Jesus and the twelve Apostles. San Galgano planted his sword in the ground, from where nobody could remove it.

The Cistercian "Abbey of San Galgano" flourished only for a very short time, already during the 14th century roving mercenaries and plagues let the convent decline.

Later the ruins were looted for building materials.