The Spiral Well (Bi'r al-Halazon) in the southern section of the Citadel, is one of four extant elements that probably date from the early Ayyubid period.
Excavated out of bedrock, the well is composed of two shafts: one from the spring to a reservoir halfway up, and the second from the reservoir to the surface. It was powered by cattle whose circumambulation brought water up to a reservoir from which it was drawn up to the surface. Medieval sources indicate that the well could be accessed by a lomg stairway, or by a path that was used for the cattle.
The well is also known as Bi'r Yusuf, or Joseph's Well, which may refer either to the Patriarch Joseph, who is connected to many sites in the area of the Citadel, or it may refer to Salah al-Din, whose first name was Yusuf.
MacKenzie, Neil D. 1992. Ayyubid Cairo: A Topographical Study. (Cairo: AUC Press), p.60-61.
Rabbat, Nasser O. 1989. The Citadel of Cairo. (Geneva : Aga Khan Trust for Culture), p. 4-5.