Tourists are usually seen standing on the edge of the sheer limestone cliff.
More than 100 metres (328ft) beneath them is a lost world of ancient forests, plants and animals. All they can see is leafy tree tops and hear is the echoes of cicadas and birds bouncing off the cliffs.
For thousands of years, this “heavenly pit” or “tiankeng”, in Mandarin, was unexplored.
People feared demons and ghosts hiding in the mists which swirled up from the depths.
But drones and a few brave souls who lowered themselves into places untouched since dinosaurs roamed the Earth have revealed new treasures – and turned China’s sinkholes into a tourist attraction.
Two-thirds of the world’s more than 300 sinkholes are in China, scattered throughout the country’s west – with 30 known tiankeng, Guangxi province in the south has more of of them than anywhere else. Its biggest and most recent find was two years ago: an ancient forest with trees reaching as high as 40m (130ft). These cavities in the earth trap time, preserving unique, delicate ecosystems for centuries. Their discovery, however, has begun to draw tourists and developers, raising fears that these incredible, rare finds could be lost forever.
Sinkholes are rare. China – and Guangxi particularly – has so many because of the abundance of limestone. When an underground river slowly dissolves the surrounding limestone rock, it creates a cave that expands upwards towards the ground.
Eventually, the ground collapses, leaving a yawning hole. Its depth and width must measure at least 100m for it to qualify as a sinkhole. Some, like the one found in Guangxi in 2022, are much bigger, stretching 300m into the earth and 150m wide.
For scientists these cavernous pits are a journey back in time, to a place where they can study animals and plants they had thought extinct. They have also found species they had never seen or known, including types of wild orchid, ghostly white cave fish and various spiders and snails.
Protected by sheer cliffs, jagged mountains and limestone caves, these plants and animals have thrived deep in the earth.