Istanbul is located in northwestern Turkey within the Marmara Region on a total area of 5,343 square kilometers (2,063 sq mi). The Bosphorus, which connects the Sea of Marmara to the Black Sea, divides the city into a European side, comprising the historic and economic centers, and an Asian, Anatolian side; as such, Istanbul is one of the two bi-continental cities in Turkey among with Çanakkale. The city is further divided by the Golden Horn, a natural harbor bounding the peninsula where the former Byzantium and Constantinople were founded. In the late-19th century, a wharf was constructed in Galata at the mouth of the Golden Horn, replacing a sandy beach that once formed part of the inlet's coastline. The confluence of the Sea of Marmara, the Bosphorus, and the Golden Horn at the heart of present-day Istanbul has deterred attacking forces for thousands of years and still remains a prominent feature of the city's landscape.