Istanbul is Turkey’s most populous city and its cultural and financial center. Located on both sides of the Bosphorus, the narrow strait between the Black Sea and the Marmara Sea, Istanbul bridges Asia and Europe both physically and culturally. Istanbul is the only transcontinental city in the entire world. On the western side of the Bosphorus Strait, you’re in Europe, but if you cross to the other side then you’re setting foot in Asia! . The city’s Grand Bazaar is the largest covered market in the world.