Colored lights illuminate the geological formations at the Benxi Water Cave, a large-scale underground karst, in Benxi, northeast China's Liaoning Province, Aug. 10, 2022. (Photo: China News Service/Yu Haiyang) Developed about 500,000 years ago, the cave has more than 400,000 cubic meters internal space and a total length of 5,800 meters. Comprising a dry cave and a water cave, it is the world's longest underground karst cave with water.

Colored lights illuminate the geological formations at the Benxi Water Cave, a large-scale underground karst, in Benxi, northeast China's Liaoning Province, Aug. 10, 2022. (Photo: China News Service/Yu Haiyang) Developed about 500,000 years ago, the cave has more than 400,000 cubic meters internal space and a total length of 5,800 meters. Comprising a dry cave and a water cave, it is the world's longest underground karst cave with water.

Colored lights illuminate the geological formations at the Benxi Water Cave, a large-scale underground karst, in Benxi, northeast China's Liaoning Province, Aug. 10, 2022. (Photo: China News Service/Yu Haiyang) Developed about 500,000 years ago, the cave has more than 400,000 cubic meters internal space and a total length of 5,800 meters. Comprising a dry cave and a water cave, it is the world's longest underground karst cave with water.

Colored lights illuminate the geological formations at the Benxi Water Cave, a large-scale underground karst, in Benxi, northeast China's Liaoning Province, Aug. 10, 2022. (Photo: China News Service/Yu Haiyang) Developed about 500,000 years ago, the cave has more than 400,000 cubic meters internal space and a total length of 5,800 meters. Comprising a dry cave and a water cave, it is the world's longest underground karst cave with water.