Neolithic settlements in central Bulgaria dating from 6000 BC are among the oldest man-made structures yet discovered. Thracian tribes entered the Balkans from the east around 1500 BC, establishing fortified villages. By 500 BC Thracian rulers were under Hellenic influence and Greek colonists founded settlements on the Black Sea coast. Thrace was conquered by Philip of Macedonia in 324 BC and later absorbed into the eastern (Byzantine) Roman Empire, along with Moesia to the north.