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 Eastern Roman Empire, which was commonly referred to by the former name of that city, the Byzantine Empire. Byzantium was colonized by Greeks from Megara in the 7th century BC and remained primarily Greek-speaking until its conquest by the Ottoman Empire in AD 1453.