In the Byzantine Empire, cities were centers of economic and cultural life. A significant part of the cities (there were more than 900 of them by the 6th century) were founded during the period of Greek and Roman antiquity. The largest of them were Constantinople, Alexandria, Thessaloniki and Antioch, with a population of several hundred thousand people. Large provincial centers had a population of up to 50,000. Although the spread of Christianity negatively affected urban institutions, in general, late antique cities continued to develop continuously. Byzantium remained an empire of cities, although the urban space had changed a lot. If the Greco-Roman city was a place of pagan worship and sports events, theatrical performances and chariot races, the residence of officials and judges, then the Byzantine city was primarily a religious center where the bishop's residence was located.