Founded by 'Amr ibn al-'As, the Muslim conqueror of Egypt, in 641-2 as a hypostyle mosque near his house, the Mosque of 'Amr ibn al-'As was rebuilt and enlarged in 673 during the reign of Mu'awiya, who is said to have added a minaret to each of its four corners.
The mosque does not exist in its original form, having undergone numerous additions and restorations through the 20th c.
Originally a hypostyle mosque, it was doubled in size in 827 with seven aisles built parallel to the qibla wall and defined by arcades on columns; the last column in each row was attached to the wall by a wooden architrave carved with a frieze of a late Hellenistic type. These architraves as well as remains of springing arches can still be seen along the southern wall of the mosque.
The tomb of 'Abdullah, son of 'Amr ibn al-'As, in the far left-hand corner of the mosque, the original site of his house and tomb, which was incorporated into the mosque in 827. Columns from churches were reused for the qibla arcade. The rearrangement of the aisles to make them perpendicular to the qibla wall is 18th c.; the columns in the entrance and side arcades, courtyard, and the fountain are 20th century.
Sources:
Behrens-Abouseif, Doris. Islamic Architecture in Cairo. Leiden: E. J. Brill, 1989.
Creswell, K.A.C. Early Muslim Architecture. n.p.: Oxford, Clarendon P., 1969.