Orsini Fortress

From http://www.trevignanoromano.it/fortress.html:

This fortification of the Orsini family which was surrounded by a double wall extending as far as the lake, defended the village. It was destroyed in 1496 by Giovanni, Cesare Borgia's brother, during the war waged against the Orsini by Pope Alessandro VI Borgia who, however, did not succeed in taking Bracciano Castle.