Istanbul 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) side of the Bosphorus, and is thereby the only metropolis in the world which is situated on two continents.
It is Turkey's most populous city (the world's 4th largest), and its cultural and financial centre. The city covers 25 districts of the province of Istanbul.
Founded in the seventh century BC, Istanbul developed in line with its position of capital city to three empires; the Eastern Roman (AD 324-395), the Byzantine (395-1453) and the Ottoman (1453-1923). Byzantium gave way to Constantinople, which in turn gave way to Istanbul. The city enjoys a noteworthy location as the meeting point between continents and a place of strategic importance. Istanbul is the leading socioeconomic and cultural center of Turkey. The city was chosen as joint European Capital of Culture for 2010, sharing the title with Essen and Pecs. The historic areas of Istanbul, including Sultanahmet Archaeological Park, Suleymaniye and Zeyrek Conservation Sites, and the Land Walls, were added to the UNESCO World Heritage List in 1985.