Constantinople was founded at the spot where an ancient Greek colony of the Megara city-state was located, named Byzantion. The ambitious building program of the new imperial residence was planned after the city model of Rome, with Agora, avenues, Hippodrome, churches and public baths. With its inauguration, the Empire's centre of gravity was transferred to the East. There, Greek culture and Hellenistic tradition were predominant, having obtained, however, a particular character in the syncretistic environment of the Near East, during a long period of coexistence with eastern civilizations. Built on a strategic spot and densely fortified by its emperors, it remained intact from deafeat by enemy forces until 1204, when it was seized and sacked by the Latins of the fourth crusade.