Istanbul (Turkish: İstanbul), historically known as Byzantium and Constantinople (see Names of Istanbul for further information) is the largest city in Turkey with a population of 13.1 million, which is 17.8% of Turkey’s population. Istanbul is also a megacity, as well as the cultural, economic, and financial centre of Turkey. The city covers 39 districts of the Istanbul province. It is located on the 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, and is thereby the only metropolis in the world that is situated on two continents. Istanbul is a designated alpha world city.
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. The historic areas of the city were added to the UNESCO World Heritage List in 1985.