Rumeli Fortress (Rumeli Hisarı)

This expansive hillside fortress on the European shoreline of Istanbul was built at the narrowest point of the Bosporus by Fatih Sultan Mehmed II—Mehmed the Conqueror—in 1452. Construction may have taken four months, but the fortress’s impact on Istanbul’s history has been eternal. These fortifications, combined with the Anadolu Fortress on the Asian shore, allowed the sultan to control supplies to the capital of the Byzantine Empire, leading to the Ottomans’ victorious Siege of Constantinople a year later.