Istanbul is the largest city in Turkey, with a population of over 15 million people. It is located on the Bosporus Strait, which connects the Black Sea to the Sea of Marmara. Istanbul is one of the oldest cities in the world, having been founded in 667 BC. It has served as the capital of the Roman, Byzantine, and Ottoman Empires. Today, it is a major cultural, economic, and financial hub in the region.