Istanbul , historically known as Byzantium  and Constantinopole . Istanbul is the largest city of Turkey. According to the address-based birth recording system of the Turkish Statistical Institute, the metropolitan municipality (province) of the city had a population of 13.26 million as of 2010which is 17.98% of Turkey's population and the 3rd largest in Europe(including its Asian half) after London and Moscow. The last census data from 2000 puts its population at 8.8 million Istanbul is a megacity, as well as the cultural, economic, and financial centre of Turkey. It is located on the Bosphorus/'>Bosphorus Strait and encompasses the natural harbour known as the Golden Horn, in the northwest of the country. It extends both on the European (Thrace) and on the Asian (Anatolia) sides of the Bosphorus/'>Bosphorus, and is thereby the only metropolis in the world that is situated on two continents. Istanbul is a designated world .

During its long history, Istanbul has served as the capital of the Roman Empire (330–395), the Eastern Roman (Byzantine) Empire (395–1204 and 1261–1453), the Latin Empire (1204–1261), and the Ottoman Empire (1453–1922). When the Republic of Turkey was proclaimed on 29 October 1923, Ankara, which had previously served as the headquarters of the Turkish  national movement during the Turkish War of Independence, was chosen as the new Turkish State's capital. Istanbul was chosen as a joint European Capital of Culture for 2010 and the European Capital of Sports for 2012. Istanbul is currently bidding to host the 2020 Summer Olympics. The historic areas of the city were added to the UNESCO World Heritage List in 1985.