In the "piazza Federico II di Svevia" there's the Norman (Swabian) Castle - the major fortified position formerly used in defense of the city. It was built in the XI Century by the Normans, who injected an intense civil and religious re-organisation into the city. This greatly stimulated maritime traffic and lifted the city out of the experiences suffered under the previous Byzantine domination. The latter took their revenge in 1156, William the Wicked putting the city to fire and sword. They even destroyed the castle, which had been built on an ancient rock as a Greek or Roman defense point. Remains of Cyclopean walls at the bottom of one of the towers can still be made out. The fortress was later re-built and enlarged by Frederick II, in accordance with has defensive policy against internal and external enemies. The primitive quadrangular nucleus of the castle thus goes back to the XIII Century. It is enclosed by four angular towers, only two of which are in respectable condition. In the last decade the foundation of the other polygonal towers were discovered to the South and East. The castle underwent a considerable amount of restoration in the Angevin period and was later further enlarged by the Spaniards, giving the powerful bastioned "coating" to the angular, lance-shaped towers. The ones facing the sea are smaller; protected from the water, they have majestic dimensions on their city-facing side. They had been built in order to adjust the fort to the new demands of war, then dominated by firearms.
This is the XVI-Century period in which Isabella of Aragon (and her daughter, Bona Sforza) took up residence in the castle, transforming it into a rich Renaissance dwelling and bestoweing splendour upon it for what was to be the last time. Indeed, after the year '500, the fort deteriorated rapidly under the Bourbons, becoming first a prison and then a barracks One of its towers situated on the left side coined the name "the minors", because from 1832 onwards underage offenders were locked up in it.