Kunming is the capital and largest city of Yunnan province in southwest China. Known as Yunnan-Fu until the 1920s, today it is a prefecture-level city and the political, economic, communications and cultural centre of the province as well as the seat of the provincial government. Kunming is also called the Spring city due to its weather. The headquarters of many of Yunnan's large businesses are in Kunming. It was important during World War II as a Chinese military center, American air base, and transport terminus for the Burma Road. Located in the middle of the Yunnan–Guizhou Plateau, Kunming is located at an altitude of 1,900 metres above sea level and at a latitude just north of the Tropic of Cancer. Kunming has as of 2014 a population of 6,626,000 with an urban population of 4,575,000, and is located at the northern edge of the large Lake Dian, surrounded by temples and lake-and-limestone hill landscapes.