Istanbul (Turkish: İstanbul, historically also known as Byzantium and Constantinople (see names of Istanbul) is the largest city in Turkey and fifth largest city proper in the world with a population of 12.6 million. Istanbul is also a megacity, as well as the cultural and financial centre of Turkey. The city covers 39 districts of the Istanbul province.[3] 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.

In its long history, Istanbul has served as the capital city of the Roman Empire (330–395), the East Roman (Byzantine) Empire (395–1204 and 1261–1453), the Latin Empire (1204–1261), and the Ottoman Empire (1453–1922). The city was chosen as joint European Capital of Culture for 2010. The historic areas of Istanbul were added to the UNESCO World Heritage List in 1985.