Istanbul is the most populous city in Turkey and the country's economic, cultural and historic center. It is located in north-western Turkey within the Marmara Region.
The Bosphorus, which connects the Sea of Marmara to the Black Sea, divides the city into a European (Thracian side), and an Asian (Anatolian side). The city is also divided by the Golden Horn, a natural harbor bounding the peninsula where the former Byzantium and Constantinople were founded.