Istanbul is a town.
Istanbul ( [ ˌɪstænˈbʊl ] , [ - ˈbuːl ] or [ - stɑːn - ] İstanbul [ isˈtɑnbuɫ ] ) , historically known as Constantinople and Byzantium , is the most populous city in Turkey and the country 's economic , cultural , and historic center . Istanbul is one of the world 's most populous cities and ranks as the world 's 7th-largest city proper and the largest European city . Arts , music , film , and cultural festivals were established at the end of the 20th century and continue to be hosted by the city today . Considered a global city , Istanbul has one of the fastest-growing metropolitan economies in the world .