The Phong Nha-Ke Bang National Park (PNKBNP) is located in central Vietnam, about 500km south of the capital, Hanoi. It is located in the Quang Binh Province at the narrowest part of Vietnam, where the hourglass-like country is only 42km wide. The western boundary of the Park forms part of the Lao-Vietnamese border, but the karst area does not end here. The continuation in Laos is called Hin Namno and Khammoune karst.
The extremely complex and ancient karst plateau with high geodiversity is covered by tropical forest with a high level of biodiversity and endemic species. The area is only sparsely explored, there is work to be done for generations of biologists, archaeologists, geologists and speleologists. The number of accessible caves which remain still unexplored is immense.
The development started in the Palaeozoic, some 400 million years ago. This makes this area the oldest major karst area in Asia. Massive tectonic movements resulted in a series of rocks that are interbedded in complex ways. Tectonic uplift and changing sea levels produced seven different major levels of karst development. There is also strong evidence of sulphurous solution and hydrothermal action.