The Castello di Lombardìa, perhaps the most important example of military architecture in Sicily. It was built by Frederick II of Sicily and restructured under Frederick II of Aragon. The castle, which bears this name because of the garrison of Lombard troops that defended it in Norman times, has an irregular layout which once comprised 20 towers: of the six remaining, the Torre Pisana is the best preserved one. It has Guelph merlons. The castle was divided into three different spaces separated by walls.