Seoul is located in the northwestern part of South Korea. The city of Seoul itself has an area of 233.7 square miles and is cut in half by the Han River, which was previously used as a trade route to China and helped the city grow throughout its history. Seoul is surrounded by several mountains but the city itself is relatively flat because it is on the Han River plain, and the average elevation of Seoul is 282 feet (86 m). Because of its very long history of settlement, Seoul is home to a number of historic sites and monuments. The Seoul National Capital Area has four UNESCO World Heritage Sites: the Changdeokgung Palace Complex, the Hwaseong Fortress, the Jongmyo Shrine, and the Royal Tombs of the Joseon Dynasty.