The Byzantium Civilization started cause of overcrowding in the eight century B.C. that led Greek city-states to send out colonies throughout the Mediterranean basin. In the year of 667 B.C.; Byzas, from the Greek city of Megra, founded Byzantium Civilization at the mouth of the Black Sea. Alexander the Great dominated Byzantium as he built an empire around it stretching from Greece to India. Byzantium was the Christianized eastern part of the Roman Empire. Constantine the Great was a vital figure in the early stages of this civilization. He established toleration for Christianity throughout the Roman Empire and legally transferred his capital from Rome to Constantinople, wh