When you live in a desert where there are no any seas, rivers or lakes, you have to get yourself out of it to survive. So did the residents of the ancient city of Kairouan: they dug huge pools to collect rainwater.

In the Middle Ages, there was no fresh or any other water in Kairouan. Locals solved this problem in a very unusual way: they built huge pools to accumulate rainwater. But it was not all that simple! The water did not just drip into the pit but went through several stages of purification process. And then, the residents finally started to scoop the water into buckets.

Medieval engineers came up with an entire hydraulic system that worked successfully for more than a thousand years. The entire installation consisted of two interconnected tanks. Water first got into one tank and then flowed into the other. First, water from the mountains in the surroundings of the city got into a small filter pool through an aqueduct. All the trash and hazardous substances remained there. The water that had already been purified flowed to a larger pool with a depth of five meters and a diameter of more than 130 meters. And finally, from this large pool, locals took water for drinking and their other needs.

The pools have been restored for tourists. According to scientists, there were about 16 of them; however, only two have been preserved to the present day. As in the past, there is still water, but it is not recommended for drinking. They look like two huge water reservoirs with low ledges in the middle of the desert, but knowing the history of this place makes it look completely different. Besides, the pools are not actually round. It was planned to make these small “lakes” in the form of heptadecagon, a seventeen-sided polygon.

You look at your own reflection on water and admire the genius of ancient engineers. Scientists still believe that this system was far ahead of its time.