Subterranean River

The Puerto Princesa Subterranean River National Park features a spectacular limestone karst landscape with its underground river. A distinguishing feature of the river is that it flows directly into the sea, and the lower portion of the river is subject to tidal influences. The area also represents a significant habitat for biodiversity conservation. The site contains a full mountain to the sea ecosystem and protects forests, which are among the most significant in Asia.
The site of the Puerto-Princesa Subterranean River National Park is located in the Saint Paul Mountain Range. It is north-west of Puerto Princesa, the capital of Palawan Province. The topography varies from flat plains to rolling hinterlands and hills to mountain peaks. Over 90% of the park comprises sharp, karst limestone ridges around Mount St Paul, which is itself part of a series of rounded, limestone peaks aligned on a north-south axis, along the western coast of Palawan.
The focus of the area is a spectacular karst landscape which features both surface karst features (pinnacles, shafts, dolines and limestone cliffs), as well as an extensive underground river system. The subterranean river is 8.2 km long, one of the most unique of its type in the world and includes many speleotherms, several large chambers exist, up to 120 m wide and 60 m high. A distinguishing feature of the river is the fact that it emerges directly into the sea, and that the lower portion of the river is brackish and subject to tidal influences.
The underground river (the Cabayugan River) arises approximately 2 km south-west of Mount Saint Paul at an altitude of 100 m, and flows underground for almost its entire length to an outflow into St Paul's Bay. All rivers and associated tributaries are within the park, which is important in relation to catchments impacts on the water quality of the Cabayugan River.