Dieppe is located in the Pays de Caux, in the deep valley of the Arques. On a promontory 98 ft (30 m) above the beach, the defensive castle of Dieppe displays a primitive tower to the west, 36 ft (11 m) in diameter with walls 6.56 ft (2 m) thick. Its construction has spanned from the 14th century to the present day. The fortress has successively served as a royal castle, barracks for soldiers, and a governor's residence. It became a prison during the French Revolution and has hosted the city's museum since 1923.