Bab al-Hadid (or the Iron Gate) was originally planned during the reign of al-Zahir Ghazi and built by his son Mohammed as Bab al-Qanat (the Aqueduct Gate). It was rebuilt by the final Mamluk sultan Qansuh al-Guri in 1509. It holds an unknown shrine within its walls.
Tabbaa, Yasser, 1997, Constructions of Power and Piety in Medieval Aleppo, The Pennsylvania State University Press, pp. 23-26.