Istanbul is the major city located on both sides of the Bosporus Strait.
The Bosporus divides Istanbul's European and Asian districts and connects the Black Sea with the Sea of Marmara. This position makes Istanbul a transcontinental city and a historic link between southeastern Europe and western Asia.
The city was founded as Byzantium, became Constantinople under the Roman and Byzantine empires, and was renamed Istanbul in common usage after the Ottoman conquest of 1453. It served as the Ottoman capital until Ankara became the capital of the Republic of Turkey in 1923.
Istanbul is Turkey's largest city, although it is not the country's capital. The Bosporus is a natural waterway, not a canal. Istanbul's European and Asian sides are connected by bridges, tunnels, ferries, and rail links, while the historic centre lies on the European side.