You can understand it is impregnable only by looking at it, as this is the only one of the medieval castles of the island that takes full advantage of the natural fortification provided by the rock on which it was built. A fortified semicircular bastion guards the main gate. Its construction was completed in 1520 during the Grand Master F. Del Carretto’s rule. The north walls, located at a point where the ground is flatter, are more fortified and sturdy. On the contrary, the south walls didn’t need to be as fortified as the north ones, because the ground is very steep at that point. According to the official records of the Knights Hospitaller that are kept in Malta, the castle was built in the early 14th century under the Grand Master H. De Villeneuve’s rule at the location of a former byzantine watchtower. Apart from that the Knights Hospitaller that were sentenced for serious offenses were imprisoned in the castle’s dungeons since 1383. The churches of Agia Paraskevi, Agios Nikolaos and the ruins of the church of Panagia Eleimonitria still exist today inside the walls of the castle. There was also a mosque inside the castle during the period of the Ottoman rule that is in ruins today.