Built in the 15C by order of the Duke of Milan to reinforce the town's defences, deemed too weak at this point, the highest of the three castles is square in shape. The terrace of the esplanade commands a fine view of the lower Ticino valley as far as Lake Maggiore. The castle is the venue for temporary exhibitions and home to a reconstitution of a fine wood-panelled room dating from the 17C.