The Mosque of Ahmad ibn Tulun is the third mosque built in Egypt in 876 and the only one to survive in its original state, and is considered the oldest.
It was converted into workshops, then into a sanatorium for the elderly, before being restored in the early 20th century.
The mosque is located on a slightly elevated area in the Sayyida Zeinab district, on Al-Khudayri Street, Cairo.
The design conforms to the traditional plan of congregational mosques in the area, and consists of a central square open courtyard approximately 92 metres long. In the middle of the courtyard is a fountain for ablutions.