İstanbul is the most populous city in Turkey and the country's economic, cultural, and historic center. Istanbul is a transcontinental city in Eurasia, straddling the Bosphorus strait between the Sea of Marmara and the Black Sea. Its commercial and historical center lies on the European side and about a third of its population lives on the Asian side.[10] The city is the administrative center of the Istanbul Metropolitan Municipality (coterminous with Istanbul Province), both hosting a population of around 20 million residents.[4] Istanbul is one of the world's most populous cities and ranks as world's 6th-largest city proper and the largest European city.