Hidden deep within the rugged landscapes of Fengjie County, China, lies one of the planet’s most astonishing natural formations—a geological wonder so vast and mysterious that it feels like a doorway into another world. This is Xiaozhai Tiankeng, also known as the Heavenly Pit, the deepest sinkhole ever discovered on Earth. Dropping an extraordinary 2,172 feet (662 meters) into the ground, it is a place where time seems to stand still and ecosystems flourish untouched by the outside world.

For centuries, this colossal chasm remained largely unknown beyond local communities. While villagers were aware of its existence, it wasn’t until 1994, when a team of British explorers accidentally came across the site, that Xiaozhai Tiankeng captured worldwide attention. Its formation is the result of millions of years of geological activity—underground rivers slowly dissolving layers of limestone until the surface collapsed, creating a vertical abyss of staggering proportions.

But the Heavenly Pit is far more than a giant cavity in the Earth. Owing to its extreme depth and shape, it has developed its own microclimate, complete with mist, cooler temperatures, and unique humidity levels. These conditions have allowed a remarkably diverse ecosystem to thrive at the bottom. To date, scientists have identified 1,285 plant species, including ancient varieties such as the ginkgo tree, as well as rare animals like the clouded leopard and the Chinese Giant Salamander, one of the world’s largest amphibians. Because of the sinkhole’s isolation, many species here may be entirely new to science.

Exploring Xiaozhai Tiankeng is an adventure reserved for the determined. The descent alone takes three to four hours, involving steep paths, rocky terrain, and continuous elevation changes. Fortunately, a 2,800-step staircase helps visitors navigate the descent safely—but reaching the bottom and climbing back to the surface is still a demanding physical challenge requiring preparation and stamina.

Its scale is almost impossible to comprehend. The Empire State Building, with all its towering height, could sit inside the pit with room to spare. At the bottom, an underground river continues to flow, silently shaping the sinkhole even today. The temperature often drops noticeably as you approach the lower levels, reinforcing the sensation that you are entering a completely different world—one untouched, ancient, and humbling.

For those curious about what it truly feels like to stand at the bottom of the world’s deepest sinkhole, the BBC has produced an immersive video giving viewers a rare glimpse into its depths. It reveals a place that feels closer to a forgotten realm from fantasy than anything found in everyday life—a testament to how little of our planet we have truly explored.