A survey team has discovered a mysterious lake in Thung cave, part of the Thoong Valley in the Phong Nha - Ke Bang National Park, a world natural heritage site in central Vietnam’s Quang Binh Province. 

Le Luu Dung, director of Junglee Boss Company Limited, located in the province’s Bo Trach District, on Friday said the firm’s surveyors had detected the new lake in a branch of the Thung cave, part of the cave system in Hung Thoong (Thoong Valley) of the park.

‘Hung’ is a local dialect that means ‘valley.’ 

With its special location – about 15m higher than the main underground river branch in the cave - the lake appears to be “hung” on the cave wall, Dung said.

Lying about a kilometer from the cave entrance, the lake has a surface area of about several hundred square meters and is surrounded with stalactite columns.

The survey team has not yet measured the depth of the lake due to lacking diving equipment, the director said.

Surveyors are trying to identify the water source that has fed this mysterious lake.

Because of the unique location of the lake, the survey team has temporarily named it ‘Lo Lung’ (Hanging) Lake.

A part of the newly-discovered lake in Thung cave, part of the Thoong Valley in the Phong Nha - Ke Bang National Park in central Vietnam’s Quang Binh Province. Photo: L. Dung / Tuoi Tre

The team will come back soon with a lot of specialized equipment to fully explore the lake. 

Hung Thoong is one of the most pristine places in the Phong Nha - Ke Bang area, with many caves located deep in the strictly protected area of the park and surrounded with a million-year-old limestone mountain system and primary forests.

The Quang Binh administration has allowed piloting tours of Hung Thoong since early 2023.

Covering an area of over 123,000 hectares in the two districts of Bo Trach and Minh Hoa, the Phong Nha - Ke Bang National Park has more than 400 caves with various sizes and shapes that have been detected so far.

The park was recognized as a world natural heritage twice by UNESCO, with the first in 2003 based on the criteria geological and geomorphological criteria, and the second in 2015 according to the biodiversity and ecological criteria.

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