Kunming is the capital and largest city in Yunnan Province, Southwest China. Known as Yunnan-Fu (云南府, Yúnnánfǔ) 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. The city 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 metres (6,234 feet) above sea level and at a latitude just north of the Tropic of Cancer. It covers an area of 21,473 square kilometres (8,291 sq mi) and its urban area covers 2,622 square kilometres (1,012 sq mi). Kunming has population of 6,432,212, including 3,583,429 in the built-up area made up of 4 urban and 1 suburban districts, and is located at the northern edge of the large Lake Dian, surrounded by temples and lake-and-limestone hill landscapes.