Its high walls survey the port. It was originally a Byzantine fortress that was later extended considerably by the Franks then the Venetians. As you walk around you will see a Byzantine chapel, the medieval prisons and the main building set up in the towers overlooking the sea. Be sure to make your way up to the rampart walk: the view over the port is splendid. The castle also houses the spectacular remains of a merchant ship from the 4C BC, which ran aground off the shore by the port.