These cisterns, built by the Aghlabids in the 9th century are more impressive because of their engineering sophistication than as sights in themselves. Water was delivered by aqueduct from the hills 36km west of Kairouan into the smaller settling basin and then into the enormous main holding basin, which was 5m deep and 128m in diameter. In the centre of the main pool was a pavilion where the rulers could come to relax on summer evenings.

Most visitors do nothing more than peek at the cisterns from the rooftop of the syndicat d'initiative office nearby, but you can enter with the multiple-site ticket.