Constantinople, now known as Istanbul, was the capital of the Byzantine Empire and later the Ottoman Empire. Founded by the Roman Emperor Constantine the Great in 330 AD, it became a major center for trade, culture, and religion. The city's strategic location between Europe and Asia made it a vital hub for commerce and military power. The city is famous for its stunning architecture, including the Hagia Sophia, a former cathedral and mosque, and the Blue Mosque. Constantinople was known for its impressive walls, which protected it for centuries, and its rich history, blending influences from both the East and the West.