The oldest part, called the chateau, was built in 1420 by the Viceroy of Corsica (then Aragonese) Vincentello d'Istria. You can wander through the old barracks, the dungeons and the Eagle's Nest tower (an attractive view over the town and the mountain). Under Louis XVI then under Louis Philippe, a first floor was constructed inside a fortified surrounding wall. The Citadel houses museums of art and history and of Corsica, the Office of Tourism and the FRAC delegation