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.