Cairo has around 400 mosques. From those, about 50 are remarkable for their rich architecture. The big ones seen here are 2 of the most important ones. The mosque of Rifai on the right and Sultan Hassan on the left are built so close as to create a knife-sharp, almost perpetually shadowed canyon bettween them (WS).
Captured from the Citadel.

Perspective of the canyon bettween the two big mosques. In the background you can see the mosque of Mohammed Ali, situated in the Citadel, which is the most touristic one, although not so impressive as expected.