A major example of military architecture from the 15th century, the castle, which is located along the Po, has an asymmetrical layout with corner towers and is encircled by a trench. Built on the request of Giovanni il Paleologo, Marquis di Monferrato, the building has been at the center of many wars and, over the course of time, has been the object of many transformations. The patrol route and the spectacular underground areas beneath the west wing, reconstructed during the 18th century, are very interesting to visit.