The scenic spot of Dujiangyan lies on the west of Dujiangyan City, Sichuan Province. It is one the largest-scale hydraulic projects constructed in ancient time and still being kept in use, while now also being one of the most well-known tourism locations in Sichuan. In 2000, Dujiangyan was listed in the UNESCO world heritages list (UNESCO site) together with Mt. Qingcheng. The dam is the oldest irrigation works in the world, built between 275 BC and 251 BC. It incorporates dam-free diversion, and has always been working perfectly, even now. The project was built under the leadership of Li Bing, Governor of Shu Prefecture in the Qin State, in order to control the flood of the Minjiang River. The irrigation system uses the way of “water diversion without a dam” and takes advantage of the natural area at a mountain pass. Ticket of Dujiangyan sight spot is RMB90/person. More info can be found via this link.