Built in 1240 by Saint Louis to establish the Kingdom of France's first Mediterranean seaport. Saint Louis embarked on the Seventh Crusade from Aigus-Mortes and then to Tunis in 1270 where he died. The castle was completed by Philip the Bold, who finished the  massive ramparts, thirty feet high and twenty feet thick containing twenty towers and ten gates. During the Hundred Years War, Burgundians captured the town but were then massacred while sleeping and their mutilated bodies thrown into what is known as The Tower of the Burgundian.

From : Castles.org