Constantinople - A Fortress?

Constantinople was the last piece of European land on the shore looking over to Asia. The city lies between the Black Sea and the Mediterranean, a sensible distance from both the Danube and Persian borders of the Empire. Out of nowhere a small inlet of sea means that the very southernmost tip is now surrounded by water on three sides. This narrow inlet, only four miles long, is called the Golden Horn. It is what turned Constantinople into such a uniquely placed city, because now only one side of it needed defensive walls.