This metropolis of 15 million occupies both sides of the entrance to the narrow, 20-mile long Bosporus Strait connecting the Mediterranean and Sea of Marmara (south) to the Black Sea (north). From its founding as Byzantium by the Greeks in 600 BC, this strategically located city has been a focus of maritime trade and commerce as well as an outpost and threshold for cultural exchange and conflict between Europe and Asia. The modern city’s layout and architecture show the influences of both the Roman-Byzantine era when it became Constantinople, the world’s first Christian capital, as well as that of the conquering Ottoman Turks, from 1453, when it became the seat of the world’s largest Muslim Empire. Today Istanbul is Turkey’s economic capital and home to nearly half the country’s wealth.