Located in China’s Chongqing Municipality, the feature has been known to local communities for centuries, a report by BBC Wildlife says.

‘Xiaozhai’ refers to a long-abandoned village nearby, while ‘Tiankeng’ translates as ‘Heavenly Pit’, the regional term used for sinkholes, the report said.

Measuring about 626 metres deep and 527 metres wide, the giant depression is so large it could dwarf familiar landmarks — it is roughly twice the height of the Eiffel Tower and significantly wider than London’s O2 Arena.

The scale of the depression is so vast that it could hold tens of thousands of Olympic-sized swimming pools, the report said.

Xiaozhai Tiankeng is believed to have formed gradually over tens of thousands of years, influenced by a combination of processes both above and below the ground.

Its distinctive two-layer structure — a wide upper basin that narrows into a smaller chamber beneath — suggests the ground likely collapsed in phases rather than at once.

Over the thousands of years that followed, the sinkhole has evolved into a self-contained natural environment.

Despite limited sunlight reaching its base, a humid, subtropical microclimate has formed, supporting a surprisingly wide variety of life, the report added.

According to the report, rare animals such as the clouded leopard have been observed here, as well as more than 1,200 plant species, including ancient ginkgo trees, ferns and mosses.

The report said that plants growing in these conditions have adapted in remarkable ways to cope with low light levels.

Compared with plants above the ground, they have lower carbon content but higher levels of nutrients such as nitrogen and phosphorus.

All of these features make Xiaozhai Tiankeng not just a geological marvel, but also a unique ecological haven — one of the most unusual and biologically rich natural environments on the planet.