This ribat dates from the 8C. From the top of the nador, or watchtower, there is a superb view of the medina, the port and the sea. The courtyard is lined with arcaded porticoes which lead to the cells once occupied by the soldier-monks. On the first floor, the cells occupy three sides of the building, while the southern side housed a prayer room. This room is plain and austere in style, with simple barrel vaults supported by large cruciform pillars and a few arrow slits providing light. According to archaeologists, this is the oldest mosque in Africa.