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 also became known by the former name of the city as the Byzantine Empire. Byzantium was colonized by Greeks from Megara in the 7th century BCE and remained primarily Greek-speaking until its conquest by the Ottoman Empire in 1453 CE.