Dujiangyan Irrigation System (都江堰, Dūjiāngyàn)

Built in 256 BCE under the engineer Li Bing, Dujiangyan does something no other ancient waterwork does: it still functions, and it has never used a dam. Li Bing's insight was to split the Min River (岷江, Mín Jiāng) with a wedge-shaped levee — the Fish Mouth (鱼嘴, Yúzuǐ) — that diverts water into an inner channel while sediment and floodwater sweep past on the outer side. It irrigates the Chengdu plain to this day and is the reason Sichuan became China's richest agricultural basin. UNESCO listed it in 2000.

Visiting is a walk rather than a monument stare. The route follows the levees past the Fish Mouth, over the Bottle-Neck Channel, and across the Anlan suspension bridge — a swaying cable-and-plank crossing high above fast green water that is the site's most photographed feature and also its most nerve-testing. Beyond it, a stone stairway climbs through cedar and gingko to Erwang Temple (二王庙, Èrwáng Miào), a multi-level Qing complex dedicated to Li Bing and his son, with the best view of the whole system laid out below.

Reality check: if hydraulic engineering leaves you cold, this can read as "a nice riverside park with some stone walls." The signage explains the mechanism reasonably well in English, but the genius is conceptual and takes a bit of imagination to appreciate. What everyone agrees on is that the setting is beautiful — the mountains actually begin here, the air is cooler than the city, and crowds are a fraction of Jinli or the panda base.

Add the nearby Dujiangyan panda base or Qingcheng Mountain if you want a full day.