The Citadel, since its foundation by Salah El-Din (Saladin), has remained the seat of Government during the rule of the Ayyubids, the Mamluks, the Ottomans, and the family of Muhammad 'Ali Pasha. Muhammad 'Ali Pasha, the founder of modern Egypt, after restoring the walls of the Citadel, built numerous palaces, schools, and government buildings. His masterpiece was the great mosque with its domes and minarets, which overlooks the city of Cairo.

The construction of this mosque was begun in 1246H. (1830) , on the site of old Mamluk buildings, and was completed in 1265H. (1848). Its decorations were completed during the reign of the late 'Abbas Pasha I. It is built in the style of the Ottoman Mosques of Istanbul. It is square in plan, and measures 41 X 41 meter; it has a centralized dome measuring 21 meter in diameter and 52 meter in height, resting on four large arches, supported by four massive piers. This dome is surrounded by four semi-domes and in the corners are four little domes. Another semi-dome covers the Mihrab on the eastern side of the mosque.

The walls and piers are lined with alabaster to the height of 11.30 m., with colored ornament above. The domes and semi- domes are decorated with painted and gilt ornament in relief. The dikka, which is supported on alabaster arches and columns is placed on the western side. The handrails of the dikka and the galleries round the domes are all made of bronze. At the south western corner is the cenotaph of Muhammad 'Ali Pasha. It has a marble mounting carved with beautiful ornament and inscriptions, and is surrounded by a beautiful decorated bronze grille, made by order of the late 'Abbas Pasha I.

There are two Minbars; the larger, which is made of wood, decorated with gilt ornament, is the original one. The smaller, which is made of alabaster, was constructed in 1358H. (1939) by order of H. M. King Farouk I. The mosque is lit by magnificent crystal chandeliers with well grouped glass lamps. At the western corners of the mosque rise two elegant cylindrical minarets of Turkish type, each being 82 m. high. The mosque has three entrances, one in the middle of each of the northern, southern, and western sides. The last one leads into a large disc, 53 sq. meters surrounded by four iwans, the arches and columns of which, together with their walls, are all lined with alabaster. In the middle of the disc is an octagonal ablution cistern covered by a carved alabaster dome, above which is a large dome supported on eight columns. This dome has an awning with raised gilt ornament, representing scenes from nature. It is covered, like the domes of the mosque, with sheets of lead.

In the middle of the western iwan is a decorated brass clock tower with a clock, which was presented in A.D. 1845 by Louis Philippe, King of France, to the late Muhammad 'Ali Pasha. The disc has two entrances, one in the northern side and the other in the southern one. The walls of the mosque have an external alabaster facing of the same height as the internal dado. Next to the northern and southern façades are two iwans, with arches and columns made of alabaster.

Towards the end of the nineteenth century, the mosque was repaired by reinforcing the four piers and bracing the masonry of the arches at their springing with iron belts. These repairs, however, were not decisive for shortly afterwards more cracks began to appear in different parts of the mosque. The condition of the mosque having become so dangerous, a scheme for its complete restoration was drawn up by order of the late King Fouad I in 1931. This scheme comprised the demolition and rebuilding, painting and gilding of all the domes. The first part of this scheme was completed during the reign of the late King Fouad I. The second part, which comprised the marble lining, painting and gilding, was completed during the reign of H. M. King Farouk I.

At the completion of this restoration, the mosque was inaugurated by H. M. King Farouk I in 1358H. (1939). The mosque has since received the personal attention of H. M. King Farouk I, who ordered the construction of the marble Minbar which stands next to the mihrab. The position of this new Minbar enables the speaker to face the whole congregation. The Qibla recess was improved by filling up its windows with alabaster. The hood of the mihrab was decorated with the word Allah in the middle, surrounded with ornament in raised relief with a gilded Quranic verse below. This mosque is one of the landmarks of Cairo and is one of the first features to be seen when approaching the city from no matter which side.