This is the oldest monument in Sousse's medina, built in the final years of the 8th century AD as a fort. It was garrisoned by devout Islamic warriors, who divided their time between fighting and silent study of the Quran in its tiny, cell-like rooms. The internal courtyard is surrounded by porticoes; in the corner is a nador (watchtower) added by the Aghlabids in AD 821; climb the narrow spiral staircase to enjoy spectacular views over the medina.
The prayer hall on the 1st floor has an elegant vaulted ceiling and reflects its dual purpose with its fortified windows that were used by archers and the simple mihrab (prayer niche in the wall indicating the direction of Mecca; this is one of the oldest in North Africa).