The tall brick clock tower at the western corner of the walls is the dominant vertical of the old town and one of the original twelfth-century corner towers of the fortress. It rises to about thirty metres and carries a fifteenth-century clock face on its southern wall — once the principal civic timepiece of the town.
Climbing the tower (open in summer for a small fee) gives the best view of the rectangular plan of the walls below, with the moat-park and the Duomo cupola visible from above. It is also the best place to take in the surrounding country: the flat agricultural plain stretches in every direction, broken only by belltowers in the distance.