The Fort was built in 1325 by Lorenzo Maitani. It sees well the three stages of construction and the materials used: the lower in sandstone, limestone in the center, brick in up. It looks like a fortification crenellated city walls inserted in the fourteenth century. In ancient times was a completion of the second circle of walls, dating from 1321. The Fort has undergone various changes over the centuries: in 1479 it was equipped with "caditoria" door, hatches and loopholes; currently houses the Museum of City Gates and Walls. From the terrace you can enjoy a beautiful view of the city and the surrounding territory.