Early in history travelers began to list and describe the marvels they saw. Ancient writers limited their lists of wonders to seven, possibly because the number seven was thought to have a special magic meaning. Two of the earliest men who described the world's wonders were Antipater of Sidon and Philon of Byzantium, both of whom lived before the birth of Christ. Only on eof the wonders they listed remains standing today. But we know something about the rest of them from other writer who saw them and from later archeological discoveries.