It was ruined by Cimmerian invaders c. 690 BC , then conquered by its neighbor Lydia , before it passed successively into the Persian Empire of Cyrus , the empire of Alexander and his successors , was taken by the king of Pergamon , and became part of the Roman Empire . Meanwhile the Phrygian Kingdom was overwhelmed by Iranian Cimmerian invaders c. 690 BC , then briefly conquered by its neighbor Lydia , before it passed successively into the Persian Empire of Cyrus and the empire of Alexander and his successors , was taken by the Attalids of Pergamon , and eventually became part of the Roman Empire .