The Nilometer is founded by the Caliph Al-Mutawakkil in 861 AD. It is considered the second Islamic sightseeing built in Egypt after Amr Ibn Al-Ass Mosque.
The Nilometer was used to measure the level of the water of the Nile River to set the taxes. The water measurement occurred by a marble octagonal column 19 cubits in length standing in the middle of the building. This meter has become unused after the building of the Aswan High Dam in the 1960s.
The structure is divided into two parts. The first part is the conical dome. The second part is a flight of spiral stairs leading down, with depth markings along the walls.