Istanbul, historically known as Constantinople and Byzantium, is the most populous city in Turkey and the country’s economic, cultural, and historic center. Istanbul is a transcontinental city in Eurasia, straddling the Bosphorus strait (which separates Europe and Asia) between the Sea of Marmara and the Black Sea. Its commercial and historical center lies on the European side and about a third of its population lives on the Asian side.
Istanbul is primarily known for its Byzantine and Ottoman architecture, but its buildings reflect the various peoples and empires that have previously ruled the city. Examples of Genoese and Roman architecture remain visible in Istanbul alongside their Ottoman counterparts. Nothing of the architecture of the classical Greek period has survived, but Roman architecture has proved to be more durable.