Istanbul is the largest city in Turkey, constituting the country's economic, cultural, and historical heart. With a population of 13.5 million, the city forms one of the largest urban agglomerations in Europe and is among the largest cities in the world by population within city limits. Istanbul's vast area of 5,343 square kilometers (2,063 sq mi) is coterminous with Istanbul Province, of which the city is the administrative capital. Istanbul is a transcontinental city, straddling the Bosphorusone of the world's busiest waterwaysin northwestern Turkey, between the Sea of Marmara and the Black Sea. Its commercial and historical center lies in Europe, while a third of its population lives in Asia. Founded on the Sarayburnu promontory around 660 BC as Byzantium, the city now known as Istanbul developed to become one of the most significant cities in history.
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