120-meter-deep, 2-hectare-wide sinkhole in Vietnam’s Phong Nha - Ke Bang publicly announced

Le Luu Dung, director of Jungle Boss, said on Thursday evening that the company had worked with experts from the U.S. National Speleological Society and the national park’s management board to survey and measure the sinkhole in the park's Cha Noi - Khe Gat area of Quang Tri Province.

“The sinkhole was surveyed a year ago, but is only now being publicly announced, and it has not yet been named,” Dung said.

Pham Hong Thai, director of the park, described the sinkhole as a new discovery that provides further evidence of the area’s karst geological system, which dates back approximately 400 million years.

He said the formation was scientifically significant for geological and geomorphological research, adding that further studies were needed.

The sinkhole has an oval-shaped opening measuring approximately 190 meters by 140 meters.

Its interior widens downward to about 250 meters long and 200 meters wide, reaching a depth of 120 meters.

Despite its size, the opening is almost concealed by the surrounding forest canopy when viewed from above.

Nguyen Van Uy, deputy director of Jungle Boss and the company’s safety director, said it was one of the largest sinkholes he had encountered during more than 20 years of exploring the forests of Phong Nha - Ke Bang.

The sinkhole was first spotted by Kevin Ditamore, a member of the U.S. National Speleological Society, who noticed an unusually large dark patch in satellite images on Google Earth.

Three drone surveys by Ditamore, other experts and Uy helped pinpoint its location.

A full survey was conducted from July 23 to 29, 2025, by a 24-member team comprising cave experts, Jungle Boss technical staff and forest rangers.

The team trekked more than 20 kilometers through the forest and across rugged limestone terrain before installing a safety rope system to descend 120 meters into the sinkhole.

At the bottom, the team recorded large limestone boulders from landslides, traces of stalactites on the rock walls and lush vegetation.

It also found monkey bones and skulls, along with vast quantities of snail shells estimated to number in the millions.

The sounds of monkeys indicated that wildlife still inhabits the area.

The team found that the limestone floor at the center of the sinkhole had been heavily eroded, leaving hundreds of fissures and cavities through which water could drain underground.

However, it found no substantial entrance to an underground cave within the surveyed area.

Ditamore said water appeared to drain through numerous cracks and small openings rather than a single large passage.

The team detected neither airflow nor a clear opening leading to an underground cave system, leaving any connection to deeper caves unconfirmed.

After the expedition, Jungle Boss submitted a detailed report and field data to the national park’s management board, proposing further research in the Cha Noi - Khe Gat area and surveys to identify additional access routes from outside the sinkhole.

The findings add to scientific knowledge of the geological and geomorphological features of Phong Nha - Ke Bang, widely known as a kingdom of caves.

According to the park’s management board, the area has 472 recorded caves with a combined surveyed length of more than 254 kilometers.

The cave network is divided into seven main areas, including three major systems: Phong Nha, Vom and Nuoc Mooc.