İstanbul is the only city that has been the capital of three empires — Roman, Byzantine and Ottoman — and the excavations at the Theodosian harbour at Yenikapı pushed its story back further still, to a Neolithic settlement 8,500 years old. That dig opened a new chapter in the archaeology of the city itself, and in what is known about its cultural and geological change.
The imperial history begins in the 4th century AD. Constantine the Great chose the site, for its strategic position, to replace Rome as the capital of an empire that had grown too large to govern from one end of it. Rebuilding took more than six years: the walls were extended and temples, government buildings, palaces, baths and a hippodrome went up. In 330 the city was proclaimed capital with great ceremony. It was called the Second Rome and the New Rome, then Byzantion, and in later centuries Constantinople — though ordinary people simply said Polis, the City.
