It features a limestone karst mountain landscape with an 8.2 km. navigable underground river. A distinguishing feature of the river is that it winds through a cave before flowing directly into the South China Sea. It includes major formations of stalactites and stalagmites, and several large chambers. The lower portion of the river is subject to tidal influences.
Until the 2007 discovery of an underground river in Mexico's Yucatan Peninsula, Puerto Princesa's underground river is reputed to be the world's longest.
The area also represents a significant habitat for biodiversity conservation. The site contains a full mountain-to-the-sea ecosystem and has some of the most important forests in Asia.
St. Paul's Subterranean River Postcard 5