Phong Nha-Ke Bang National Park

Phong Nha-Ke Bang National Park, in Vietnam's north-central coast region about 500 kilometers south of Hanoi, protects one of the world's two largest karst regions, with roughly 300 caves and grottoes set within the limestone forest of the Annamite Range. Its core zone covers about 858 square kilometers, within a wider UNESCO World Heritage Site of some 217,447 hectares inscribed in 2003 for its geological significance. The park contains Son Doong Cave, considered the largest cave in the world, with a single chamber exceeding five kilometers in length, and its karst landscape, among the oldest in Asia, includes formations dating back some 400 million years to the Paleozoic era. Tropical forest covers about 96 percent of the protected area, sheltering rare primates, endangered orchids and species such as the saola.