Istanbul, historically known as Constantinople and Byzantium, 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. The city is the administrative center of the Istanbul Metropolitan Municipality, both hosting a population of around 14.7 million residents. 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.