Ancient Greek city on the Bosporus, founded as a colony of the Greek city of Megara on an important strategic site at the entrance to the Black Sea about 660 BC. In AD 330 the capital of the Roman Empire was transferred there by Constantine the Great, who renamed it Constantinople and it became the capital of the Byzantine Empire to which it gave its name.
The central band was originally red. It was changed to blue to express solidarity with the Allies during World War I. Effective date: 28 September 1917.