The karst formation of Phong Nha-Ke Bang National Park has evolved since the Palaeozoic
(some 400 million years ago) and so is the oldest major karst area in Asia.
Subject to massive tectonic changes, the park's karst landscape is extremely complex
with many geomorphic features of considerable significance. The vast area, extending
to the border of the Lao People's Democratic Republic, contains spectacular formations
including 65 km of caves and underground rivers.
In summary, Phong Nha displays an impressive amount of evidence of earth's history.
It is a site of very great importance for increasing our understanding of the geologic,
geomorphic and geo-chronological history of the region.