Hidden beneath the forest canopy of Phong Nha – Ke Bang, a vast sinkhole has been documented in the Chà Nòi – Khe Gát area. The park’s management board estimates its area at about 2.18 hectares and its depth at 100–120 metres. From above, the opening is framed by dense forest; below, steep limestone walls descend toward a pocket of green.

How the Sinkhole Was Found

The first clue came from satellite imagery. Kevin Ditamore, a cave specialist and member of the National Speleological Society (NSS), noticed an unusual landform in the Chà Nòi – Khe Gát area. Follow-up checks using drones helped locate it and prepare a route for a field survey.

After an initial reconnaissance in April 2025, a 24-member team returned from 23 to 28 July. The survey brought together NSS specialists, Jungle Boss staff and members of the national park’s forest protection force. Reaching the site meant crossing rugged forest terrain before the team could establish safety lines and examine the areas accessible to them.

This was a specialist field survey in a strictly protected zone, not a recreational expedition or a tourist visit.

A Vast Opening and an Inverted-Bowl Shape

Preliminary measurements describe an oval opening roughly 190 metres long and 140 metres wide. The surveyed area is estimated at 2.18 hectares, while the sinkhole reaches about 100–120 metres deep. The interior is broader in places, measuring approximately 250 metres in length and 200 metres across, according to the survey team’s initial observations.

Its limestone walls widen toward the bottom, giving the formation the appearance of an inverted bowl. The team recorded fallen rock and signs of landslides along parts of the walls, which made some areas difficult to inspect. Although sinkholes are associated with changes in karst terrain over time, further geological work is needed to explain how this particular formation developed.

A Green Pocket Beneath the Limestone

The depth is only part of what makes the site striking. Forest vegetation grows between the limestone walls and scattered rocks, creating a vivid contrast with the sheer stone around it. During the survey, the team noted signs of monkeys near the rim, as well as shells and traces of stalactites. These are preliminary observations; specialist surveys would be needed to identify the area’s species and understand its ecology.

The survey team did not find an accessible cave entrance leading farther underground, nor a clear stream or airflow that would point to a connected cave system. Fallen material may conceal openings, but the available evidence is not enough to confirm whether an underground network exists. That unanswered question is part of the site’s scientific interest—and a reason more research is needed before drawing conclusions.

Discover Phong Nha Beyond the Sinkhole

The Chà Nòi – Khe Gát sinkhole lies in a strictly protected area of Phong Nha – Ke Bang National Park and is not currently open to visitors. Travelers can still experience the region’s landscapes through established attractions: take a boat along the Son River into Phong Nha Cave, wander among the formations of Paradise Cave, or spend time by the river at Chay River – Dark Cave.

When your time is limited, fitting transport, cave visits and activities into a few days can quickly turn planning into another task. Phongnha Discovery Tours can help you shape an itinerary around your schedule and interests, leaving more room to enjoy the journey between the limestone mountains, rivers and forests.

Explore Phong Nha tours with Phongnha Discovery Tours – a trusted tour operator based in Phong Nha – and find a trip that fits the pace and experiences you want from your visit.