Istanbul is a town.
Istanbul . Istanbul is a transcontinental city in Eurasia , straddling the Bosphorus strait ( which separates Europe and Asia ) between the Sea of Marmara and the Black Sea . 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 . Founded under the name of Byzantion on the Sarayburnu promontory around 660 BCE , the city developed to become one of the most significant in history . Approximately foreign visitors arrived in Istanbul in 2015 , five years after it was named a European Capital of Culture , making the city the world 's fifth most popular tourist destination . Considered a global city , Istanbul has one of the fastest-growing metropolitan economies in the world .