History and significance

The limestone of Phong Nha-Ke Bang began forming approximately 400 million years ago during the Devonian period, when this region lay beneath a shallow tropical sea. The dissolution of carbonate rock by weakly acidic groundwater over geological time created a labyrinth of passages, chambers, and sinkholes that remains only partially explored. Vietnamese cavers and the British Cave Research Association have been the principal surveyors; the most celebrated discovery came in 2009, when a team led by Howard Limbert confirmed that a cave entrance found by a local farmer in 1991 led to a passage of unprecedented dimensions — Son Doong, the world’s largest cave.

Human presence in the region is ancient. Cham Hindu temples dating to the 9th–10th centuries CE survive within the park, testimony to the Cham Kingdom’s northern extent along what is now the Vietnamese coast. In the 20th century the park’s cave systems acquired an entirely different significance: during the Vietnam War (1965–1975), dozens of cave passages were used by North Vietnamese Army units and the Viet Cong as shelters, hospitals, storage depots, and supply-convoy waypoints on the Ho Chi Minh Trail. Several caves still contain traces of this use — rusted equipment, blackened walls from cooking fires, carved inscriptions.

The park’s biodiversity is also exceptional. Species found nowhere else include several new-to-science mammals and amphibians discovered during post-1986 surveys, as the previously closed region became accessible after the Doi Moi reforms.