Istanbul is the largest city in Turkey, constituting the country's economic, cultural, and historical heart. Its commercial and historical centre lies in the European part of Eurasia, while about a third of its population lives in the Asian part. With a population of 14.1 million, the city forms the largest urban agglomeration in Europe as well as the largest in the Middle East, and the sixth-largest city proper in the world. Istanbul's vast area of 5,343 square kilometres is coterminous with Istanbul Province, of which the city is the administrative capital. Istanbul is a transcontinental city, straddling the Bosphorus strait in northwestern Turkey between the Sea of Marmara and the Black Sea.