The imposing castle, surrounded by deep moats, stands on the site of two older royal residences. It was built in 1279 by the architects of Charles Ist of Anjou, Pierre de Chaulnes and Pierre d'Agincourt, based on the model of the castle of Angers.
The splendid Triumphal Arch of Alphonso the Magnanimous contrasts with the austerity of the fortress. It was built according to the plans of Francesco Laurana and placed at the castle entrance, facing the town, in 1467. The Arch is decorated with sculptures to the glory of the House of Aragon.
Inside, the Barons' room contains a superb ribbed, vaulted ceiling. It is nowadays used to host Municipal Council meetings.
The Palatine Chapel is all that remains of the original castle. It is entered through an elegant, Renaissance door. In the West Wing, the castle contains collections from the Museo Civico, mainly paintings, sculptures and objets d'art from the 14C to 19C, illustrating the turbulent history of Naples.
Above the castle, there is a magnificent view over the city.