Istanbul (Turkish: İstanbul), historically known as Constantinople (See Names of Istanbul for further information) is the largest city in Turkey and 5th largest city proper in the world with a population of 12.8 million, also making it the second largest metropolitan area in Europe by population, and the largest metropolitan city proper. 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, the city previously served as the capital city of the classical (330–395), "Byzantine" (395–1204 & 1261–1453), and "Latin" (1204–1261) Roman Empires and the Ottoman Empire (1453–1922), prior to the selection of Ankara as the capital of the new Republic of Turkey during the Turkish War of Independence. The city was chosen as joint European Capital of Culture for 2010. Historic areas of Istanbul were added to the UNESCO World Heritage List in 1985.
Byzantium (Greek: Βυζάντιον, Byzántion) is the first known name of the city. Around 660 BC,[note 1] Greek settlers from the city-state of Megara founded a Doric colony on the present-day Istanbul, and named the new colony after their king, Byzas. After Constantine I (Constantine the Great) made the city the new eastern capital of the Roman Empire in 330 AD, the city became widely known as Constantinopolis or Constantinople, which, as the Latinised form of "Κωνσταντινούπολις" (Kōnstantinoúpolis), means the "City of Constantine". He also attempted to promote the name Nea Roma ("New Rome"), but this never caught on. Constantinople remained the official name of the city throughout the Byzantine period, and the most common name used for it in the West until the establishment of the Republic of Turkey.
By the 19th century, the city had acquired a number of names used by either foreigners or Turks. Europeans often used Stamboul alongside Constantinople to refer to the whole of the city, but Turks used the former name only to describe the historic peninsula between the Golden Horn and the Sea of Marmara. Pera was used to describe the area between the Golden Horn and the Bosphorus, but Turks also used the name Beyoğlu, which is still in use today. However, with the Turkish Postal Service Law of 28 March 1930, the Turkish authorities formally requested foreigners to adopt İstanbul, a name in existence since the 10th century, as the sole name of the city within their own languages.
Etymologically, the name "İstanbul" (Turkish pronunciation: [isˈtanbuɫ], colloquially [ɯsˈtambuɫ]) derives from the Medieval Greek phrase "εἰς τὴν Πόλιν" [is tin ˈpolin] or, in the Aegean dialect, "εἰς τὰν Πόλιν" [is tan ˈpolin] (Modern Greek "στην Πόλη" [stin ˈpoli]), which means "in the city" or "to the city". In modern Turkish, the name is written "İstanbul", with a dotted İ, as the Turkish alphabet distinguishes between a dotted and dotless I. Also, while in English the stress is on the first syllable ("Is"), in Turkish it is on the second syllable ("tan"). Like Rome, Istanbul has been called "The City of Seven Hills" because the oldest part of the city is supposedly built on seven hills, each of which bears a historic mosque.