The Puerto-Princesa Subterranean River National Park features a spectacular limestone karst landscape located on the island of Palawan, Philippines. One of the distinctive features of this underground river is that it emerges directly into the sea and its lower part is subject to tidal influences. The area also represents an important habitat for the conservation of biodiversity, the site contains a full ‘mountain-to-sea’ ecosystem and has some of the most important forests in Asia.