Rumeli Hisarı and Anadolu Hisarı, the Twin Fortresses That Closed the Bosporus Before 1453
The Bosporus is at its narrowest, about 700 metres, between Aşiyan on the European shore and Kandilli on the Asian one. Two Ottoman fortresses face each other across it there. Together they show, in stone, why whoever holds this stretch of water holds the Black Sea.