Istanbul historically known as Byzantium is the capital city of the homonymous province and the main industrial, financial and cultural center of Turkey.

With a population of around 15 000 000 inhabitants, Istanbul (also considering the Asian neighborhoods) is the second most populous municipal center in Europe (sixth in the world) in front of London and behind Moscow.

Istanbul is a megalopolis located in the north-west of the country, which extends along the Bosphorus Strait, at whose southern end lies the natural port of the Golden Horn, and along the northern shores of the Sea of ​​Marmara. The city, divided by the Bosphorus, extends both in Europe (Thrace) and in Asia (Anatolia), resulting in the only metropolis in the world belonging to two continents. Istanbul is considered a global city.

During its long history, the city (called Byzantium up to 330, then Constantinople until 1453, Istanbul or Constantinople until 1930, and from then on only Istanbul) was the capital:

of the Roman Empire (330-395);
of the Byzantine Empire (395-1204 and 1261-1453);
of the Latin empire (1204-1261);
of the Ottoman Empire (1453-1922).
Also known by the name of “second Rome”, it was one of the largest cities of Christianity until the Ottoman conquest in 1453, becoming for nearly five hundred years the capital of one of the greatest empires of history and crossroads of cultures . When the Republic of Turkey was proclaimed on October 29, 1923, Istanbul was now considered too vulnerable, being endangered by navies that had shown to be able to violate the Straits during the First World War, and so Ankara, who previously had served as the headquarters of the Turkish citizen movement during the Turkish war of independence, it was chosen as the capital of the new Turkish state.

In 2010 Istanbul was one of the European capitals of culture. Since 1985, the historical areas of Istanbul are part of the UNESCO list of World Heritage Sites.