At their height of power the Celtic Empire stretched over the ancient world from Ireland and Britain to Turkey and Czechoslovakia, from Belgium and Gaul to Spain and Italy. They sacked Rome, invaded Greece, and even attempted to conquer the Pharaohs of Egypt. Yet theirs was an empire without an emperor, a civilization that encompassed the continent but had no central government. The religion of the Celts, led by a priesthood known as the Druids, was described by ancient writers as crude and violent. Druids served as priests and religious leaders, but also as judges and sacrificers. Celts had a reputation as headhunters as they saw the human head as the center of the emotions as well as of life itself.