Byzantium () or Byzantion () was an ancient Greek city in classical antiquity that became known as Constantinople in late antiquity and Istanbul today. The Greek name "Byzantion" and its Latinization "Byzantium" continued to be used as a name of Constantinople sporadically and to varying degrees during the thousand year existence of the Byzantine Empire. Byzantium was colonized by the Greeks from Megara in 657 BC, and remained primarily Greek-speaking until its conquest by the Ottoman Empire in AD 1453.