The citadel was built by the Visconti in the 13C but quickly passed into the hands of its current owners, the Borromeo family, in 1449. Among its historic rooms, which are furnished and decorated, admire the courtroom decorated with admirable 14C frescoes evoking the life of archbishop Ottone Visconti. The fortress is also home to a doll and toy museum, one of the largest museums of its kind in Europe. Sweeping views can be enjoyed from the Castellana tower.