Byzantine Empire, Empire, southeastern and southern Europe and western Asia. It began as the city of Byzantium, which had grown from an ancient Greek colony founded on the European side of the Bosporus. The city was taken in 330 ce by Constantine I, who refounded it as Constantinople. The area at this time was generally termed the Eastern Roman Empire. The fall of Rome in 476 ended the western half of the Roman Empire, and the eastern half continued as the Byzantine Empire, with Constantinople as its capital. The eastern realm differed from the west in many respects: heir to the civilization of the Hellenistic era, it was more commercial and more urban. Its greatest emperor, Justinian (r. 527–565), reconquered some of western Europe, built the Hagia Sophia, and issued the basic codification of Roman law. After his death the empire weakened. Though its rulers continued to style themselves “Roman” long after Justinian’s death, “Byzantine” more accurately describes the medieval empire. The long controversy over iconoclasm within the eastern church prepared it for the break with the Roman church (see Schism of 1054). During the controversy, Arabs and Seljuq Turks increased their power in the area. In the late 11th century, Alexius I Comnenus sought help from Venice and the pope; these allies turned the ensuing Crusades into plundering expeditions. In the Fourth Crusade the Venetians took over Constantinople and established a line of Latin emperors. Recaptured by Byzantine exiles in 1261, the empire was now little more than a large city-state. In the 14th century the Ottoman Turks began to encroach. Their extended siege of Constantinople ended in 1453, when the last emperor died fighting on the city walls and the area came under Ottoman control.