Constantinople

Ancient city founded by the Greeks as Byzantium in about 660 BC and refounded by the Roman emperor Constantine (I) the Great in AD 330 as the capital of the Eastern Roman Empire. Constantinople (modern Istanbul, Turkey) was the impregnable bastion of the Eastern Roman Empire and the Byzantine Empire, its successor, until it fell to the Turks on 29 May 1453 after a nearly two-month siege and became the capital of the Ottoman Empire.

For over a thousand years the walls established by the emperors of Rome and of the Eastern Empire defended the city against all assailants. Nothing is known of the early defences before Constantine began construction of fortifications to protect his new capital; these ran in an exterior arc from the present-day Atatürk Bridge to the Istanbul Hospital, but have not survived.