Kunming is the political, economic, communications and cultural center of Yunnan, and is the seat of the provincial government. It is also home to several universities, museums, galleries and other important economic, cultural, and educational institutions. The headquarters of many of Yunnan's large businesses are in Kunming as well. 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 m above sea level and at a latitude north of the Tropic of Cancer. It covers an area of 21,501 km² and its urban area covers 6,200 km². Kunming has an estimated population of 5,740,000 including 3,055,000 in the urban area and is located at the northern edge of the large Lake Dian, surrounded by temples and lake-and-limestone hill landscapes.