Cave explorers in the Guangxi region of China have found a secret ancient forest hidden inside a 630-foot-deep sinkhole.
As seen in a Twitter video posted by the China state-affiliated media organization CGTN earlier this month, the karst sinkhole — formed by rainwater that dissolves bedrock — exceeds 5 million cubic meters in area.
Inside, explorers found a primeval forest with ancient trees measuring 130 feet in height, Chinese outlet Xinhua News reported.
30th giant karst sinkhole discovered in south China's Guangxi pic.twitter.com/52ZxFnyuWF
— CGTN (@CGTNOfficial) May 11, 2022
The outlet added that it took the expedition team several hours to reach the bottom of the sinkhole, after they rappelled down almost 330 feet.
Team leader Chen Lixin told Xinhua that the plants they found at the bottom grew densely together, coming up to his shoulders.
The explorers referred to the sinkhole as "tiankeng" in Mandarin, or "heavenly pit," AccuWeather reported.
RELATED VIDEO: Sinkhole Collapse - Security Footage Video 2
Never miss a story — sign up for PEOPLE's free daily newsletter to stay up-to-date on the best of what PEOPLE has to offer, from juicy celebrity news to compelling human interest stories.
"I wouldn't be surprised to know that there are species found in these caves that have never been reported or described by science until now," George Veni, executive director of the National Cave and Karst Research Institute in New Mexico, told AccuWeather Wednesday.
"Because of local differences in geology, climate, and other factors, the way karst appears at the surface can be dramatically different," he added.
"So in China, you have this incredibly visually spectacular karst with enormous sinkholes and giant cave entrances and so forth. In other parts of the world, you walk out on the karst, and you really don't notice anything. Sinkholes might be quite subdued, only a meter or two in diameter. Cave entrances might be very small, so you have to squeeze your way into them."
The Twitter video specified that the recent find brings China's number of this type of sinkholes to 30.
It also mentioned that the newest sinkhole originated from an underground river system called Fugui, while the previous 29 came about from the Bailang underground river.
The country is also home to the world's largest sinkhole, known as the Xiaozhai Tiankeng in Chongqing's Tiankeng Difeng National Park.