Built from 1402 by the Knights Hospitaller, the castle is easily the most prominent landmark in the city. The castle now operates as a museum, with the focus on the Museum of Underwater Archaeology (see below). It is one of the world's best preserved monuments dating back to medieval times. The supervision of the construction of the castle was assigned to the German architect Heinrich Schlegelholt, so that the latest developments in castle design were included. The castle is quite pretty and the views are spectacular.