Istanbul is a human settlement.
The city today known as Istanbul has been the site of human settlement for approximately three thousand years . 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 .