Built on the banks of Lake Dian and surrounded by limestone mountains; Kunming was an important ancient trade route between Tibet; China and Southeast Asia. The city; then called Yunnanfu; suffered at the hands of rebel leader Du Wenxiu; the Sultan of Dali; who attacked and besieged the city several times between 1858 and 1868; razing most of the city's Buddhist temples. In the 1890s; an uprising against working conditions on the Kunming-Haiphong railway line saw 300;000 laborers executed after France shipped in weapons to suppress the revolt. The railway line; only completed in 1911; was built by the French so that they could tap Yunnan's mineral resources for their colonies in Indochina. Today; Kunming is a city of over 6 million people; and is the political; economic; communications and cultural centre of Yunnan.