 Complete the following phrase:  Byzantium was never a major influential city-state like that of Athens, Corinth or Sparta, but the city enjoyed relative peace and steady growth as a prosperous trading city lent by its remarkable position. The site lay astride the land route from Europe to Asia and the seaway from the Black Sea to the Mediterranean, and had in the Golden Horn an excellent and spacious harbor. Already then, in Greek and early Roman times, Byzantium was famous for the strategic geographic position that made it difficult to besiege and capture, and its position at the crossroads of the Asiatic-European trade route over land and as the gateway between the Mediterranean and Black Seas made it too valuable a settlement to abandon, as Emperor Septimius Severus later realized when he razed the city to the ground for supporting Pescennius Nigers 