The findings were announced following an expedition involving experts from the US National Speleological Society (NSS), adventure tourism operator Jungle Boss and the park’s management board to survey the sinkhole in the Cha Noi–Khe Gat area.

The sinkhole has an oval-shaped opening measuring about 190 metres wide and 140 metres long. It widens towards the bottom, reaching about 250 metres in length and 200 metres in width, with a depth of around 120 metres.

According to Le Luu Dung, director of Jungle Boss, the sinkhole was first identified through satellite imagery research. While examining the terrain on Google Earth, Kevin Ditamore, an experienced expert from the NSS, spotted an unusual dark area amid the limestone mountains and forests. Based on this clue, the research team conducted three drone surveys to pinpoint the location.

Earlier, on April 27, 2025, a 10-member team, including two local forest rangers, began a trek to find a route to the sinkhole. However, the rugged terrain, scarce water supplies and difficult travel conditions forced the team to turn back on the third day, shortly after reaching the sinkhole's rim.

Following further preparations, a 24-member expedition comprising cave specialists, Jungle Boss technical staff and forest rangers returned from July 23 to 29, 2025, to conduct a more detailed investigation.

The team travelled more than 20km through dense forest and across rugged limestone mountain ranges, with limited access to drinking water.

At the site, the specialists used specialised equipment and installed safety ropes to descend into the sinkhole, enabling them to measure its dimensions and document its geological characteristics.

One of the most striking findings was a thriving natural ecosystem at the bottom, including numerous large, mature trees. The expedition also recorded substantial accumulations of seashells and snail shells near the rock faces, along with numerous monkey bones. These findings could provide material for further research into the area’s geological development, past environmental conditions and wildlife.

The team also examined the rock walls for evidence of a connection between the sinkhole and the surrounding underground cave system.

The specialists found a fissure about 5m high and extending 12–15 metres into the rock. No airflow was detected through the opening, while areas near the foot of the rock face and locations showing signs of water flow had been buried by debris from previous landslides. Consequently, the expedition was unable to establish a direct connection between the sinkhole and any other cave system.

The survey adds to knowledge of the geological, geomorphological and ecological features of Phong Nha-Ke Bang National Park, which is renowned for its extensive limestone formations, underground rivers and complex cave networks. The park was inscribed on UNESCO’s World Heritage List in 2003./.