Istanbul (historically Byzantium and Constantinople), is the largest city of Turkey, home to a population of 8,803,468 in 2010. A megacity, it is the nation's cultural, economic, and financial center, ranked as an alpha(-) world city by GaWC in 2010.
Located in the northwest of the country, it lies on the Bosphorus strait and encompasses the natural harbour known as the Golden Horn. Extending both on the European (Thrace) and Asian (Anatolia) sides of the strait, Istanbul is the only city in the world situated on twocontinents. It covers 39 districts of Istanbul province. The greater Istanbul metropolitan area held 18% of Turkey's population in 2010. Its 13.26 million residents rank it third in Europe after those of London and Moscow.
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 new Republic of Turkey was proclaimed in 1923 Ankara was chosen as its capital.
Istanbul's historic areas were added to the UNESCO World Heritage List in 1985. It was named 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.