Built between 1015-1016, the Mosque of al-Lu'lu'a (the Pearl) is one of several small mosques built on the Muqattam Hill that are attributed to the reign of al-Hakim.
The tower-like mosque was rectangular in plan with three levels, with the ground-floor walls built of local limestone blocks with a rubble core. The arches were constructed of brick and stone, the upper levels and the vaults were constructed of brick, and the interior walls were probably plastered.
The ground floor was partly excavated from the rock of the hill, and was barrel vaulted with unornamented mihrab in the rear wall and a triple-arched entrance facade. The central level was also barrel-vaulted, had an ornamented mihrab, and was lit by a rectangular window. The uppermost level was divided into two rooms, each probably lit by one window.
The facade and vaults of the mosque collapsed in 1919, but the mosque was recently rebuilt by the Dawoodi Bohras.
Creswell, K. A. C. 1979. The Muslim architecture of Egypt. New York : Hacker Art Books, 113-115.