Sultan Ahmed Al Mansour built this fortress in 1582 to monitor the populace of Fez. Modelled on Italian forts, the building holds a display of European and Middle Eastern weapons, a model of the Bou Inania water clock and an interesting section on Fez's late-19th-century mechanised arms factory. There's a great view from the roof. Drawbacks: it's a long way from the medina (there's no direct walking path) and signage is in French and Arabic only. Beware the midday closing.