Kuang Si Falls is a staircase of milky-turquoise pools stepping down through the jungle about 29 kilometres south of Luang Prabang. The main drop pours some 60 metres off a forested cliff, and below it the water spreads into terrace after terrace, each pool held in by its own low rim of pale stone. The colour comes from limestone dissolved in the stream rather than from any trick of the light, and because that mineral is still being laid down, the shape of the falls shifts slowly from year to year. It is the most visited natural sight in northern Laos.
Wooden walkways and dirt paths climb from pool to pool, and on a hot day you can wade into the lower basins, where the water stays cool and glows aquamarine over a white streambed. Higher up, spray from the main drop drifts through the trees and chills the air around it. Some of the upper pools are held sacred by local people and closed to swimmers, so visitors gather in the broad lower terraces instead. Near the entrance, a sanctuary run by Free the Bears has taken in dozens of rescued Asiatic black bears since 2003. These are moon bears saved from bile farms and the wildlife trade, dozing in forest enclosures beside the path. The colour is best in the dry months from November to April, when the flow settles and runs clearest; through the monsoon the falls swell into a brown, roaring torrent that hides the blue until the rains ease.