Citadel of Saladin and Muhammad Ali Mosque, Cairo — Saladin began this fortress in 1176 AD to hold off the Crusaders. Nine centuries later it still dominates Cairo's eastern skyline. The Muhammad Ali Mosque inside, built 1830–1848, was deliberately modeled on the great mosques of Istanbul. Nine centuries of military and religious power on a single hilltop.
© Silar, CC BY-SA 4.0, via Wikimedia Commons