Istanbul historically known as Constantinople and Byzantium, is the most populous city in Turkey and the country's economic, cultural, and historic center. Istanbul is a transcontinental city in Eurasia, straddling the Bosphorus strait (which separates Europe and Asia) between the Sea of Marmara and the Black Sea. Its commercial and historical center lies on the European side and about a third of its population lives on the Asian side. The city is the administrative center of the Istanbul Metropolitan Municipality has a population of around 15 million residents.
Istanbul's strategic position on the historic Silk Road, rail networks to Europe and the Middle East, and the only sea route between the Black Sea and the Mediterranean have produced a cosmopolitan populace, although less so since the establishment of the Turkish Republic in 1923. Overlooked for the new capital Ankara during the interwar period, the city has since regained much of its prominence.
Approximately 12.56 million foreign visitors arrived in Istanbul in 2015, making the city the world's fifth most popular tourist destination Istanbul has one of the fastest-growing metropolitan economies in the world. It hosts the headquarters of many Turkish companies and media outlets and accounts for more than a quarter of the country's GDP.
As expected for a city of its size, Istanbul has a diverse industrial economy, producing commodities as varied as olive oil, tobacco, vehicles, and electronics. Despite having a focus on high-value-added work, its low-value-added manufacturing sector is substantial, representing just 26 percent of Istanbul's GDP, but four-fifths of the city's total exports. The only Turkish stock exchange is located in Instanbul.