Sultan Salah al-Din al-Ayyubi commissioned his vizier, Baha al-Din Qaraqush, to build a well supplying the citadel with water in the southwestern side of al-Nasir Muhammad ibn Qalawun Mosque. The well was known as “Yusuf’s Well” after the name of Salah al-Din (Salah al-Din Yusuf ibn Ayyub). It was also known as "The Spiral Well" and "The Citadel’s Well". It was dug at the same time as the castle building 572-589 AH / 1176-1193 AD.
The well is characterized by an architectural design with foreign influences. It was dug in the rock at a depth of about 90 m, and it consists of two floors, around which a spiral staircase, narrows at the bottom of it. On each floor, there is a water wheel that raises water by cattle, its walls contain apertures for lighting and ventilation.
According to historians, the water that comes from the well was pure at the beginning, until Qaraqosh wanted to increase its water, so he expanded in digging the mountain, and a salty spring came out of it that changed its pureness. Hence, Salah al-Din al-Ayyubi constructed barrages to transport water from the Nile to the Citadel throughout the Ayyubid period to be continued in Mamluk period known as the Cairo Citadel Aqueduct.