Kairouan

Founded in 670 as the first Arab base in North Africa, Kairouan's Great Mosque established the plan — square minaret, hypostyle prayer hall, courtyard — that mosques across the Maghreb and Spain then followed. Tradition holds that seven pilgrimages here equal one to Mecca, and the city's cisterns, built in the ninth century, still show how a town of this size survived in semi-desert.