Founded by Frederick II of Swabia in the eighteenth century, the Castle had a certain visibility during the Sicilian Vespers as the seat of Parliament, and later, residence of the Kings of Aragon. Today it houses the Civic Museum. It is square-shaped, with circular towers at the four corners and walls made of random length of lava rock. The north side is the main, well-preserved, with four windows. The entrance is topped by a sculpture depicting a niche with Swabian eagle clutching a hare, symbol of King Frederick II. Here stood the drawbridge and the walls, the remains of which are visible into the moat. The south side has changed over time: until the mid-sixteenth century was directly overlooking the beach, then, the construction of the St. George's Bastion and the Platform of Santa Croce it away from the sea, making it efficient for use of the guns. The east side has a wonderful Renaissance window with five-pointed star made of lava stone. Modern restoration work brought to light part of the bastions, a sentry box and the original footings. It was developed within a beautiful courtyard with Renaissance staircase outside the Catalan-Gothic style. Around the courtyard there were four large rooms lined with smaller rooms, from which access was gained to the corner towers. The period when the Castle was used as a prison trace remains in the hundreds of graffiti that fill every room of the ground floor.