A 630-foot-deep sinkhole in China is hiding a pristine ancient forest

Watch your step.

A gigantic ancient forest was found tucked away inside an enormous sinkhole inside the Guanxi region of China, according to an initial Xinhua News report.

Incredibly, the sinkhole is more than 1,000 feet (304.8 m) long, and nearly 630 feet (192 m) deep, said Senior Engineer Zhang Yuanhai of the Institute of Karst Geology at China's Academy of Geological Sciences, in the report.

South China's landscape is naturally sinkhole friendly

When they came across the big dip in the jungle, the cave explorers rappelled down more than 328 feet (100 m) to reach the bottom of the sinkhole. When they landed in its murky depths, they looked up to take in what turned out to be a primeval forest filled with ancient trees that reach at least 130 feet (40 m) high, according to the expedition's team leader, Chen Lixin — who also said the plants grew in an extremely dense formation, and were tall enough to bristle his shoulders.

Some of this was documented in a video captured by a drone and posted to Twitter on May 7 that depicted the explorers making their way through the super-dense plant life.

These undisturbed sinkholes often house unseen species of flora and fauna. "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," said Executive Director George Veni of the National Cave and Karst Research Institute, based in New Mexico, in a Wednesday AccuWeather report.

Sinkholes are called tiankeng in Mandarin, which in English means "heavenly pit." And they are abundant in South China, thanks to the landscape itself — which is called karst. This phenomenon comes into being when rainwater breaks down bedrock, said Veni in a Live Science report.

Sinkholes are typically 'subdued', and much smaller

"Because of local differences in geology, climate, and other factors, the way karst appears at the surface can be dramatically different," said Veni, in the Live Science report. "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," Veni continued. "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 area of the new sinkhole was placed on the UNESCO World Heritage list for unique topography in 2007 — which is brimming with bizarre rock formations and sprawling cave formations. But in terms of sheer scope, the most gigantic sinkhole in the world is also in China. Called the Xiaozhai Tiankeng and more than 2,000 feet deep, it persists in relative sanctity within Tiankeng Difeng National Park, inside Chonqing City.

Sinkholes are often grim news as the increasingly distressing pace of global climate change causes some to form from a rapid change in temperature, or the toll that follows a building collapsing as its support gives way to a big hole in the ground. So it's great to hear of sinkholes that not only preserve the parts of nature we love, but keep relics of its ancient past alive for us to explore, study, and understand.