New 3-kilometer Hang Thang cave discovered in Phong Nha - Ke Bang National Park

A six-day survey inside the strictly protected zone of Phong Nha - Ke Bang National Park has recorded a previously unmapped cave about 3 kilometers long, with chambers widening to more than 100 meters in places, Jungle Boss said after returning from an expedition in the Ma Da Valley.

The cave has been named Hang Thang after the local forest-goer who first reported the entrance. Jungle Boss is also using the English name Victory Cave, a reference to the nearby Road 20 Quyet Thang, one of the historic routes connected with the Ho Chi Minh Trail.

The expedition began on June 3, 2026, after a local resident told Jungle Boss about a cave entrance in an area the company already knew well. Jungle Boss then worked with the Management Board of Phong Nha - Ke Bang National Park to organize a technical survey.

What the team found was larger than expected.

Preliminary mapping shows Hang Thang runs for roughly 3,000 meters. Its average width is about 70 meters, with several sections opening beyond 100 meters. The height from the cave floor to the ceiling averages around 50 meters, and some chambers rise to an estimated 70 to 80 meters.

The cave sits in the Ma Da Valley, between Elephant Cave and Ma Da Lake, in Thuong Trach Commune, Quang Tri Province. The same area is already known to adventure travelers through guided routes such as the Elephant Cave and Ma Da Valley Jungle Trek, but Hang Thang itself is not open to visitors.

A small entrance, then a much larger cave

Hang Thang does not announce itself from the surface. The entrance is a dark opening of about 5 square meters near the top of a limestone mountain. To reach the floor, the team had to rig ropes and rappel about 20 meters down a vertical wall.

Nguyen Van Uy, Jungle Boss deputy general director and safety director, said the first sound test from the entrance suggested a major void below.

"When I shouted down, the sound came back loudly and stayed for a long time," Uy said.

Even after the team reached the cave floor, the scale was hard to judge. Headlamps could not reach the far walls in some sections. As the survey team moved deeper, the cave widened and split into two branches. It has two entrances, including a narrow exit passage that fits only one adult at a time.

The approach was also difficult before anyone reached the cave mouth. The surrounding mountain is covered with sharp karst rock, locally known as "tai meo" limestone. Moving rope systems, survey equipment and safety gear across that terrain was one of the hardest parts of the expedition, according to the survey team.

An expedition member stands at the entrance to the newly discovered Hang Thang cave in Phong Nha - Ke Bang National Park

Formations recorded during the first survey

Inside Hang Thang, the team documented large stalagmite and stalactite systems, including columns estimated at up to 50 meters high. Survey members also recorded flowstone, cave curtains, rimstone pools and an unusually high number of cave pearls.

The cave pearls drew particular attention. Uy said the cave pearls inside Hang Thang are the largest he has seen in caves previously surveyed by the team. The cave also has a bright white ceiling formation that stands out from the surrounding rock. Jungle Boss said the color may be linked to a higher concentration of calcium in that part of the cave.

Giant cave pearls found inside Hang Thang cave during the Jungle Boss survey

Three large rimstone pools were also found inside. Their presence is one reason the team suspects there may be an underground water system connected with Ma Da Lake, although that has not yet been confirmed. Hang Thang is currently described as a dry cave with a downward-sloping structure, but water movement during the rainy season may explain how the calcium pools continue to form.

Nguyen Xuan Huong, Jungle Boss product development director, said the cave is estimated to have formed about 4 to 5 million years ago. That estimate is preliminary and will need further geological assessment.

The team also noted several animal skeletons inside the cave. Near the entrance, survey members found traces suggesting that people may once have reached the cave mouth to collect water. Those signs were limited to the entrance area, with no evidence that earlier visitors moved deep into the cave.

A large chamber inside Hang Thang, where preliminary survey data recorded sections more than 100 meters wide.

Why the discovery surprised the team

The Ma Da Valley is not a blank spot on Jungle Boss maps. The company has operated in the wider area for years, and its guides know the surrounding forest, caves and water systems well.

That familiarity made the report from the local forest-goer easy to doubt at first. When he described the entrance, Uy suspected it might be a cave mouth the team had already checked. The description was close enough to known terrain that the team could have dismissed it. Instead, they organized a verification trip.

Six days later, the team came out with preliminary survey data for a major cave.

The result says something practical about Phong Nha - Ke Bang: even familiar valleys can still hide large cave systems. Dense forest, sharp limestone and protected core zones make exploration slow, technical and heavily regulated.

Large stalactite and stalagmite formations inside Hang Thang cave, recorded during the first survey.

What happens next

Jungle Boss said it has submitted a proposal to the National Park Management Board and relevant authorities to consider adding Hang Thang to the Ha Ma Da Valley - Tra Ang Cave Eco-Adventure Tour project.

That does not mean the cave will open soon.

Further surveys are planned before any tourism route can be approved. Jungle Boss said the next stage will include more detailed mapping, safety assessment, geological review and conservation planning. The company also plans to work with specialists from the United States during the next phase of product development.

If Hang Thang is approved for limited tourism in the future, the route is expected to sit around Level 3 out of 6 on the Jungle Boss adventure difficulty scale. Level 3 routes in Phong Nha generally require guided trekking, helmets, headlamps, river or cave movement, and a higher level of supervision than ordinary sightseeing.

The company's current cave tours in Phong Nha do not yet include Hang Thang.

Access remains restricted

Hang Thang is inside a strictly protected zone of Phong Nha - Ke Bang National Park. Independent access is not allowed, and the entrance requires technical rope equipment.

Jungle Boss said its main concern after announcing the cave is unauthorized access. Cave formations can be damaged quickly. A hand placed on a growing stalactite, a footstep inside a calcium pool, or a change to a cave's microclimate can disrupt processes that took thousands or millions of years to build.

Jungle Boss CEO Le Luu Dung inside Hang Thang cave, where conservation planning will shape any future tourism proposal

If tourism is approved later, the company said visitor numbers, group frequency, guide protocols and walking routes would need approval from park authorities. Areas with dense formations, rimstone pools and cave pearls would be protected with fixed paths, observation points and route markers to keep people away from fragile surfaces.

Those measures are consistent with the company's published environment protection and survival rules, which require guests to stay on designated routes and avoid touching cave formations.

For now, Hang Thang remains a surveyed discovery rather than a travel product. The first map gives park officials and cave specialists a starting point. The decision on whether people should ever enter it as visitors will take longer.