The Dujiangyan Irrigation System is originally constructed around 256BC by the State of Qin as an irrigation and flood control project, it is still in use today. The system’s infrastructure is on the Min River,the longest tributary of the Yangtze. The area is in the west part of the Chengdu Plain, at the confluence between the Sichuan basin and the Tibetan plateau.The Dujiangyan, the Zhengguo Canal in Shaanxi and the Lingqu Canal in Guangxi are collectively known as the "three great hydraulic engineering projects of the Qin."Mount Qingcheng is a mountain in Dujiangyan, Sichuan, China. It is considered one of the birthplaces of Taoism and one of most important Taoist centres in China. It is home to Dujiangyan Giant Panda Center and is a UNESCO World Heritage site.At a height of only 1,260 meters (4,133 feet), Mount Qingcheng is one of the best day trekking options surrounding Chengdu.