The Phou Hin Poun National Biodiversity Conservation Area, formerly known as the Khammouane Limestone National Biodiversity Conservation Area, is one of 21 National Biodiversity Conservation Areas of the Laos. Located in a limestone tower karst region of the Annamite Range in Khammouane Province, it is home to a number of rare or newly discovered species. The Hinboun river flowing out of a nondescript opening at the base of a towering cliff hints there may be something wondrous inside. It is in fact 7.5 kilometres of wonder—a river passage through solid rock, and travellers can traverse the entire length to the other side on an exhilarating boat ride. This is Konglor Cave, a highlight of Laos.