The Dujiangyan Irrigation System is one of the oldest hydraulic engineering projects in the world still in operation. Built in 256 BC by Li Bing, the Qin-dynasty governor of Shu, it diverts the fast-flowing Min River into an inner channel feeding the Chengdu Plain and an outer channel for flood management. No dam wall was ever used — the system relies entirely on the geometry of the diversion, a brilliance that meant it survived the 2008 earthquake largely intact while modern Zipingpu Dam upstream suffered significant damage.
The site is organised around three main features: the Yu Zui (Fish Mouth) diversion island in the middle of the river, the Feisha Spillway that automatically flushes excess sediment, and the Baopingkou (Bottle-Neck Channel), a narrow gorge cut through a mountain to control water flow. Iron bars set into the riverbed still mark the minimum and maximum water levels Li Bing's engineers established. Walking the suspension bridges and embankments gives a real sense of the scale; the roar of the river at high water is impressive.
The park surrounding the works is well laid out. Enter from the south gate for the most logical route through the system. Allow two to three hours. Admission includes the walk to Erwang Temple on the hill above.