The Cistercian Abbey of San Galgano was built between 1224 and 1288 near the site of the former hermitage of San Galgano (1148-81).
Galgàno Guidotti was born into a high-ranking family in Chiusdino. As a youth, he led a life of dissipation until he had a vision of the Archangel Michael calling him to take holy orders. When his friends tried to persuade him to return to his old ways he plunged his sword into a stone (where it remains to this day) to show that he had fully renounced his earlier life. Guidotti joined the Cistercians and ended his days as a hermit. He died in 1181 and was canonised in 1185.
The abbey quickly grew in wealth and became allied with the Republic of Siena. Its monks presided over the construction of the cathedral in Siena. However, in the second half of the 14th century a long period of decline set in. In 1363 the abbey was sacked by the condottiere, Sir John Hawkwood, and his men. By the end of the century only the abbot remained. The abbey eked out an existence for nearly four centuries, but in 1786 the campanile collapsed, taking with it the roof of the church. The abbey was duly abandoned and its ruins were looted for building material.
A short walk from the abbey lies the Eremo di Montesiepi, which was built on the site of the ancient hut, where San Galgano spent the last year of his life. The hermitage (eremo) was begun in 1182 and consecrated in 1185.
The Eremo di Montesiepi is home to the famous sword in the stone.