The Byzantine Castle was remodeled before 1317 by the Knights of St John . Except for a few parts of the Byzantine fortification, there is nothing still standing from before the time of the Knights. They rebuilt the fortifications from the beginning, making many changes and improvements. The few towers follow the natural conformation of the cliff. There was a pentagonal tower on the south side commanding the harbour, the settlement and the road from the south of the island. There was a large round tower on the east facing the sea and two more, one round and the other on a corner, on the northeast side of the enceinte. Today one of the towers at the southwest corner and one to the west of the Governor's Palace still survive. On the 30th of December 1522 the castle surrendered to the Turks. During the 16th and 17th centuries the use of cannon in warfare made it necessary to construct bastions at the three corners of the castle. A small Turkish garrison, which occupied it until 1844, carried out a few minor building works of a military nature.