The mosque is said to have been built on the site of Amr Ibn el-As's tent at Fustat, is the oldest existing mosque, not just in Cairo, but the entire African Continent. Located north of the Roman Fortress of Babylon, it is actually on the edge of Fustat, the temporary city founded by Amr, and was an Islamic learning center long before El-Azhar Mosque. It could hold up to 5,000 students.
The mosque was originally built on an area of 1,500 square cubits, overlooking the Nile. The initial structure was quite simple; with walls bare of any plaster or decorations, but without niche (miharb), minaret or ground cover. It had two doors on the north and two others facing Amr's house.
The mosque area remained unchanged until 672 AD (53 AH), when Musallama al-Ansari, Egypt's ruler on behalf of Caliph Mu'awiya Ibn abi-Sufian undertook expansion and renovation works for the mosque. Walls and ceilings were decorated and four compartments for "muezzins" (callers for prayers) were added at the corners, together with a minaret, while the mosque ground was covered with straw mats.
In 698 AD (79 AH), the mosque was demolished and expanded by Abdul-Aziz Ibn Marwan, Egypt's ruler. Once again in 711 AD (93 AH), the mosque was demolished by Prince Qurrah Ibn Shuraik al-Absi, Egypt's ruler. Upon the orders of Caliph al-Waleed Ibn Abdul-Malek, the mosque area was enlarged, a niche, a wooden pulpit (minbar) and a compartment and copings of four cloumns facing the niche were gold-coated. The mosque had then four doors to the east, four to the west and three to the north.
Under the Abbasid state, successive additions and repairs were introduced. In 827 AD (212 AH), Abdullah Ibn Taher, Egypt's ruler on behalf of Caliph al-Ma'moun ordered an equivalent area to the north to be added to the mosque, thus bringing its total area to its present level of 13,556,25 square metres. (112.3m x 120.5m). However, the Fatimid period was the gold era for the mosque, where gilted mosaics, marble works, a wooden compartment and a moving pulpit were introduced and part of the niche was silver-coated.
The last structural amendments in Amr Mosque were made during the rule of Murad Bey under the ottoman era, in 1797 AD (1212 AD). Because of the collapse of some columns, the interior of the mosque was demolished and rebuilt. As a result, eastern arcades were repositioned so as to be perpendicular to the mihrab wall. Accordingly, arches were extended across windows. Two minarets were built and are still extant. Amr Mosque was not merely a place of worship but also served as a court for settling religious and civil disputes. Moreover, teaching circles were organized either for general religious preaching or teaching lessons in Quranic sciences, jurisprudence and Prophet Muhammad's Tradition (Hadith) as well as letters.
The mosque incorporates elements of Greek and Roman buildings, and has 150 white marble columns and three minarets. Simple in design, its present plan consists of an open sahn (court) surrounded by four riwaqs, the largest being the Qiblah riwaq. There are a number of wooden plaques bearing Byzantine carvings of leaves, and a partially enclosed column is believed to have been miraculously transported from Mecca on the orders of Mohammed himself. There are many other ancient legions related to the Mosque.