Imperial residence, founded in 324 by Constantine  the Great on the site of Byzantium. Bounded to the north by the Golden Horn, with the Bosporus  to the east and the Hellespont to the south, the city could only be attacked from one side by land. By virtue of its site it dominated trade and commerce between Europe and Asia, between the Aegean and the Black Sea ( Pontos Euxeinos; Hdn. 3,1,5; Pol. 4,38-45).