Istanbul is the only major city in the world located on two continents.

Istanbul straddles the Bosphorus Strait, the narrow waterway that separates Europe from Asia and connects the Black Sea to the Sea of Marmara. The city’s historic core and about two-thirds of its population sit on the European side, while a substantial and densely populated portion of the city lies across the strait on the Asian side, linked by bridges and an undersea rail tunnel.

This geography made Istanbul, known through history as Byzantium and later Constantinople, one of the most strategically valuable cities in the world for millennia, sitting directly on the trade and military routes between Europe and Asia. No other city of comparable size and global significance is split across two continents the way Istanbul is, which is part of why control of the city was contested by successive empires for over a thousand years.