The Aghlabid pools are considered to be among the most important and famous hydraulic installations in the Islamic world. They are part of an array of fifteen or so other pools located outside the wall of Kairouan that supplied the city with water.
The magnificence of these impressive hydraulic installations fascinated Arab historiographers and geographers, who visited Kairouan in the Middle Ages, which earned it the title of 'Madinat al Mawajil' (the City of Cisterns).
The pools are fed by rainwater runoff, as well as by some of the Wadi Margallil tributaries, which at times of flooding, flow into the surrounding depressions.
The vast majority of the Kairouneses have wells and drinking water cisterns at home; water stored in the pools is therefore used to meet the water needs of the population, and particularly the most destitute, during periods of drought; they were also used to supply caravans and to water the livestock.
The pools were built during the reign of the Aghlabid prince Abû Ibrâhîm Ahmad between 246 and 248 of the hegira / 860 and 862 AD. They are built of rubble stone covered with thick plaster and consist of three basic components: a small decantation pool, a large storage pool, and two cisterns for drawing water.
The small pool: 17 m in diameter, it is surrounded by a polygonal wall supported by seventeen internal and twenty-six external alternating buttresses, which are intended to consolidate the building and increase its capacity to resist the pressure of water. These are semi-cylindrical buttresses topped by a hemisphere. With a capacity of 4,000 m3. this pool is meant to remove impurities from water. Once it has been settled, the water flows into the large basin through a discharge outlet called Esarh (Arabic for discharge).
The large pool: Polygonal in shape, 128 m in diameter, this pool is supported on the inside and outside by rounded rubble buttresses (64 on the inside and 118 on the outside). It is 4.80 m deep with a storage capacity exceeding 57,000 m3. In the middle of this pool stands a poly-lobed pillar which was once topped by a dome and used by rulers to relax. This large pool is used to store the water needed to cover daily needs. However, the storage allows for better purification of the water, the most purified part of which is used as drinking water, stored in drawing cisterns.
Drawing cisterns: Consisting of two parallel reservoirs connected upright to the large pool, they are covered with barrel vaults, supported by arches resting on pillars. The capacity of each of these cisterns exceeds 1000 m3.
Built to meet a vital need, the Aghlabid pools stand out by their impressive dimensions and by their unique architectural style, characterized by their sturdiness and the harmony of their volumes. They are the expression of the city's struggle against drought and water shortage.