Cascading down the flanks of the Ailao Mountains in southern Yunnan, more than 3,000 individual terraces at some locations step from forested ridgelines to the valley floor, forming one of the most extensive and enduring feats of traditional agricultural engineering anywhere in the world. The Honghe Hani Rice Terraces, built and continuously maintained by the Hani ethnic minority for an estimated 1,300 years, were inscribed as a UNESCO World Heritage cultural landscape in 2013, recognized both for their scale and for the ingenious four-part ecological system that makes them possible at all.
The terraces occupy a landscape with no natural lakes or major rivers to draw on directly, so the Hani solved their water problem by capturing it at the source. Forests preserved above roughly 2,000 meters elevation catch monsoon rainfall, which seeps through the mountain's geology — clefts in surface rock channel it downward, while a layer of sandstone beneath the granite traps the water and gradually releases it as natural springs. From there, a communally maintained network of four trunk canals and 392 branch ditches, totaling some 445.83 kilometers in length, distributes water down through village settlements to the terraced fields below, all without pumps or modern infrastructure.