Istanbul is the largest Turkish city which is the country's economic and cultural centre.
Istanbul has a unique geographical position on both sides of the Bosporus Strait and along the Sea of Marmora straddling the boundary between Europe and Asia.
The city dates back to 658 BC when it was called Byzantium. Later known in history as Constantinople (since the 4th century AD), it was renamed Istanbul after being conquered by the Ottoman Sultan Mehmet II in 1453. Throughout its history it was the capital of powerful empires: the Roman, Byzantine and Ottoman. The city is replete with architectural landmarks of various epochs, including the world-famous Byzantine churches of St Sophia and Hora, more than 50 mosques of the Ottoman period including the Blue Mosque. The most popular museums are the Sultan's palaces Topkapi and Dolmabahce. Perhaps the best known site in the city is one of the largest indoor markets in the Middle East (Kapali Charsi).
Greater Istanbul has a population of 12.5 million (the unofficial figure is 18 million). The burgeoning population aggravates old and creates new problems, including safety, unemployment, housing, water supply, power supply, transportation and so on.
The European and Asian parts of the city are connected by the largest suspended automobile bridge in Europe (1,358 metres long, opened in October 1973). In 1988 the second suspended bridge, more than 1 km long, was opened for traffic. The building of a railway tunnel under the Bosporus started in May 2004 and a third bridge across the strait is being planned.
The Istanbul industrial region accounts for over 35% of Turkey's industrial output, 40% of its trade, 23% of Turkey's GNP, about 60% of export and import transactions. More than half of the 500 major Turkish trade and industrial companies have headquarters in Istanbul. The Istanbul Chamber of Industry is the largest in the country and the Istanbul Chamber of Commerce is the oldest in Turkey. Istanbul is the home of one of the largest organizations of Turkish private business, the Turkish Society of Industrialists and Business People (TUSIAD). The Istanbul Stock Exchange has been operating since 1986.
Istanbul is also one of the most important tourist centres in Turkey, a transit hub for tourists bound for the country's holiday resorts.
The city holds leading positions in cultural and educational fields. It has the Istanbul University, Bosporus University, the Universities of Marmara, Sinan, Yildiz, the Istanbul Technical University, the Jerrahpasha Medical University, Galatasaray Lyceum and others.
Historically, Istanbul is an important religious centre. Along with Islamic institutions and mosques the city has the Constantinople (Ecumenical) Orthodox Patriarchy, the Armenian Patriarchy, several Catholic churches and Jewish Synagogues.
Istanbul has 109 consular missions (47 general consulates, one consulate and 61 honorary consulates).