Istanbul, is the largest city in Turkey, straddling the Bosporus Strait, the boundary between Europe and Asia. It is considered the country's economic, cultural and historic capital. The city has a population of over 15 million residents, comprising 19% of the population of Turkey, and is the most populous city in Europe and the world's fifteenth-largest city.
Istanbul is in north-western Turkey and straddles the Bosporus Strait, which provides the only passage from the Black Sea to the Mediterranean via the Sea of Marmara. Historically, the city has been ideally situated for trade and defense: The confluence of the Sea of Marmara, the Bosporus, and the Golden Horn provide both ideal defense against enemy attack and a natural toll-gate. Several picturesque islands-Büyükada, Heybeliada, Burgazada, Kınalıada, and five smaller islands-are part of the city. Istanbul's shoreline has grown beyond its natural limits. Large sections of Caddebostan sit on areas of landfill, increasing the total area of the city to 5,343 square kilometers (2,063 sq mi).
Despite the myth that seven hills make up the city, there are, in fact, more than 50 hills within the city limits. Istanbul's tallest hill, Aydos, is 537 meters (1,762 ft) high.