Borromeo Castle, Medieval castle at Peschiera Borromeo, Italy.

Borromeo Castle is a former fortified farmhouse in Peschiera Borromeo, transformed in the 15th century by Vitaliano I Borromeo. It has a water-filled moat, four corner towers and a taller central tower above the entrance, preceded by a ravelin. The surrounding land was marshy and the modest size suggests prestige and family protection rather than military aims.

In 1432 Duke Filippo Maria Visconti granted Vitaliano I Borromeo the right to fortify his "cassina de la Peschera", a rural farmstead. The Borromeo banker had earlier lent the Ospedale Nuovo 180 gold florins and gradually acquired its Mirazzano holdings. The fortified farm became known as the castle of the Peschera, named after the fish pond beside it.

The name "Peschiera" comes from the fish pond beside the fortified farm, where fish were once raised; the Borromeo family, bankers to Duke Filippo Maria Visconti, took the site over in the 1430s. Visitors today see the four corner towers and the central tower above the entrance, still ringed by spring-fed water.

The exterior walls can be viewed from a walking path that leads from the nearby village. The interior is not open to visitors, but the surrounding structure is visible and can be observed from the outside.

The water system has been maintained continuously since its original construction 600 years ago. Very few fortified residences in Lombardy have preserved their historic water defenses to this day.