We’ve previously written about an astonishing newly discovered sinkhole in China that revealed a primeval ‘lost world’ hidden beneath the surface. But this next geological wonder takes the concept to a completely new level—literally and figuratively.

Welcome to Xiaozhai Tiankeng, also known as the Heavenly Pit—the world’s deepest sinkhole. Nestled in Fengjie County, in China’s Chongqing Municipality, this jaw-dropping natural formation plunges an astonishing 2,172 feet (662 meters) straight down into the Earth’s crust. To put that into perspective, that’s deep enough to swallow the Empire State Building with room to spare.

A Hidden Wonder Revealed

For centuries, Xiaozhai Tiankeng remained cloaked in mystery. While local villagers may have known of its existence, it wasn’t until a team of British explorers stumbled upon it during an expedition in 1994 that the sinkhole came to the attention of the global scientific community.

What makes this sinkhole even more remarkable is how it was formed. Over millions of years, underground rivers carved their way through the region’s limestone bedrock, slowly dissolving it and creating vast caverns below. Eventually, the surface collapsed, revealing the massive void we see today—a stunning example of karst topography at its most extreme.

An Isolated Ecosystem

But the Xiaozhai Tiankeng is far more than just a giant hole in the ground. It contains an entirely unique microclimate, complete with its own weather patterns, misty clouds, and lush, thriving vegetation. Scientists have documented 1,285 species of plants, including ancient trees like the ginkgo, growing along its walls and floor.

Even more fascinating is the wildlife. Rare and endangered species such as the elusive clouded leopard and the Chinese giant salamander—one of the world’s largest amphibians—have been found in this secluded environment. Because of its remote and relatively untouched nature, researchers believe the sinkhole could harbor species never before recorded by science, making it a living laboratory for biological and ecological discoveries.

A Journey Into the Depths

Visiting the Xiaozhai Tiankeng is not for the faint of heart. The descent into the sinkhole can take up to 4 hours, requiring a physically demanding trek along steep and uneven terrain. The return trip is equally challenging, if not more so. Fortunately, there’s a 2,800-step staircase built into the rock, offering some assistance for adventurers willing to make the journey.

Proper gear, stamina, and sometimes a guide are highly recommended. The extreme depth and isolation mean conditions can change rapidly, and the environment inside is often cooler and more humid than the surrounding areas—another quirk of its microclimate.

The Living Sinkhole

What truly sets the Xiaozhai Tiankeng apart is its scale and continued evolution. Deep beneath its floor, an underground river still flows, contributing to the ongoing formation of the sinkhole. Experts believe that this subterranean water system could lead to further collapses over time, slowly reshaping the landscape even more.

Standing at the bottom of this vast natural cathedral, surrounded by towering walls of stone, mist-shrouded trees, and the sounds of hidden wildlife, is like stepping into another world—a forgotten world untouched by modern civilization.

Want to See It for Yourself?

Curious to know what it feels like to descend into the planet’s deepest sinkhole? The BBC Reel has produced a short but stunning video offering an inside look at Xiaozhai Tiankeng, capturing its breathtaking scale and mysterious beauty. It's a must-watch for anyone fascinated by the natural wonders of our world.