Phong Nha-Ke Bang National Park

Phong Nha-Ke Bang National Park is a vast karst region in central-northern Vietnam that contains some of the world's most significant cave systems and is recognised as one of the great remaining karst landscapes on Earth.

The park was inscribed on the UNESCO World Heritage List in 2003 in recognition of its outstanding geological and ecological value, following a nomination process that began in 1998. It covers approximately 123,326 hectares of the Bo Trach District in Quang Binh Province, close to the border with the Laos People's Democratic Republic, and is part of a contiguous karst belt that extends across central Vietnam and into neighbouring countries.

The name Phong Nha refers to the Phong Nha cave, a seven-kilometre river cave known since pre-colonial times and mentioned in Vietnamese historical records dating to the nineteenth century. Adjacent to it lies the Hang Khom cave, and the park contains more than 300 documented caves spanning a combined length of over 100 kilometres. In 2013 the park was expanded to include Son Doong cave, the largest known cave passage in the world by volume, approximately nine kilometres in length with sections reaching 200 metres in height and 150 metres in width. The cave contains its own internal ecosystem, weather systems, and a jungle where a collapsed ceiling allows sunlight to penetrate deep into the cave floor. The second-largest cave in the complex, Hang En, reaches approximately three and a half kilometres in length.

Geologically, the karst of Phong Nha-Ke Bang has formed over 400 million years of marine carbonate deposition and subsequent tectonic uplift, producing a complex three-dimensional landscape of interlocking hills, sinkholes, and underground river systems. The park supports substantial areas of old-growth karst forest that provide habitat for rare primate species, including the critically endangered Hatinh langur, as well as numerous birds, reptiles, and amphibians. The local ethnic minorities in the surrounding villages, predominantly the Van Kieu and Bru-Van Kieu peoples, have lived in and around the karst landscape for generations, maintaining agricultural practices and cultural traditions shaped by the cave environments.

Access to the main caves requires a guided boat trip along the Son River, which flows through the Phong Nha cave entrance and provides the primary means of entry into the underground system. Above ground, hiking trails through the karst forest lead to viewpoints over the limestone outcrops and to the Tra Ang river cave, another significant formation in the park system.

It contains Son Doong, the largest known cave passage in the world by volume, a subterranean landscape of its own internal weather, jungles, and rivers.

The Phong Nha cave system itself, at seven kilometres, is one of the longest river caves in Asia and can be explored by boat.

The karst forest surrounding the caves is home to critically endangered primate species found nowhere else on Earth.