From my visit to the site in the summer of 1971. Rumelihisarı (“Roman Fortress”) was built in 1451-1452 by Sultan Mehmet II (“The Conqueror”) on the west side of the Bosphorus north of the city walls of Constantinople. With its counterpart Anadoluhisari (“Anatolian Fortress”) on the Asian side of the strait it cut off all access to the city from the north during the siege of Constantinople in 1453.