This imposing building was originally the fortress of Castrum Anglaris, the medieval fortified town that went on to become modern-day Anghiari. It was originally three metres higher, with ramparts, and loomed over the small town from every angle. The original nucleus of the building included the ancient Abbey of San Bartolomeo,which had been transformed into a fort by the Perugians between 1337 and 1347. After Anghiari was conquered by the city of Florence, there was no more need for a fort in the town, so it was transformed into a monastery. During restoration work in 1956, many 12th- and 13th-century elements of the building were discovered.