Istanbul, formerly known as Constantinople, is the largest city in Turkey, serving as the country’s economic, cultural and historic hub. The city straddles the Bosphorus strait, lying in both Europe and Asia, and has a population of over 15 million residents, comprising 19% population of Turkey. Istanbul is the most populous European city and the world’s 15th largest city. It is home to several UNESCO World Heritage Sites, and hosts the headquarters of numerous Turkish companies, accounting for more than thirty percent of the country’s economy.