The ingenuity of this irrigation system prevented disastrous flooding in the area. The system was constructed in 250 BC on the upper slopes of Minjiang River. The system is inclusive of a network of earth dams that branch out into tributes and canals in order to irrigate the fields. As was the intention behind building this fantastic system, the area hasn't been flooded in nearly 2,200 years, and it has also resulted in the Chengdu Plain being one of the fertile regions in China. While you are there appreciating the effects of Dujiangyan Irrigation System, you can take the tour to nearby Mount Qingchengsahn. The cave found at the top of the mountain is said to be used by Zhang Daoling, the founder of the Taoist religion.