Beneath a mountain lies America’s largest underground lake - and no one knows how deep it goes

In Tennessee’s Great Smoky Mountains National Park, deep within the Craighead Caverns, lies one of modern geography’s enduring mysteries. Known as the Lost Sea, it is the largest underground lake in the United States, the second largest in the world, and the only one whose true depth remains unknown to this day.

At first glance, the lake measures 800 feet long and 220 feet wide. But the phrase “at first glance” is critical here. Those dimensions account only for the visible portion of the lake. The real mystery lies beneath the surface. No one has yet been able to determine how deep it actually goes. For Jules Verne, it might well have been a gateway to the center of the Earth.

Numerous divers have launched exploration missions equipped with sonar systems and cutting-edge technology, yet all have returned without finding the bottom. The lake is a labyrinth, a potentially deadly trap that branches into a network of tunnels as it descends. Those passageways lead to additional tunnels, and the process repeats several times before each ultimately opens into water-filled chambers. Adventurous explorers have ventured into some of them, but not all. The result is the impression of a body of water with no end.

For years, the title of the world’s largest underground lake has generally been associated with Dragon’s Breath Cave in Namibia. Its depth is also the subject of debate, though it is estimated to cover roughly five acres of water with a depth approaching 330 feet. The Lost Sea, by comparison, spans about 4.5 acres, but its depth remains a mystery, hence the name. Many believe that once its bottom is finally reached, it could challenge its African rival for the crown.

Found by a teenaged boy

The lake was discovered in 1905 by a 13-year-old boy who had ventured into the caves to play. The youngster crawled through a narrow tunnel for more than 40 feet before suddenly dropping into the lake. Fortunately, he landed in a section where the water was only knee-deep. That boy, Ben Sands, made it out safely and reintroduced the world to a remarkable place that has served countless purposes throughout human history.

Archaeologists and explorers have uncovered a remarkably diverse collection of artifacts inside the Lost Sea caves. There are deposits of gunpowder and saltpeter left behind by Confederate soldiers who likely used the caverns as a wartime storehouse. Pottery, arrowheads, and other Indigenous artifacts point to Cherokee inhabitants who may have sought refuge there. Researchers have also found organic remains left by European settlers who appear to have used the caves for storage, along with footprints and bones belonging to a giant Pleistocene jaguar that measured more than six feet long and weighed around 500 pounds.

And that is without mentioning the spectacular stalagmites, stalactites, and rock formations, some of which date from approximately 2.5 million years ago to the end of the last Ice Age around 11,700 years ago.

Open to visitors

Exploration efforts largely came to an end in the 1970s, and today the site has become one of Tennessee’s premier tourist attractions. Visitors to Craighead Caverns can choose from a variety of guided tours and even take a boat ride across the surface of the lake itself.

During periods of drought, water levels have dropped by more than 30 feet, raising a number of intriguing questions. Beyond the mystery of how deep the lake truly is and what may lie hidden at its bottom, there is also the issue of how climate change and increased human activity could affect The Lost Sea, one of the few places in nature that continues to resist complete understanding.

Get closer to the game! Whether you like your soccer of the European variety or that on this side of the pond, our AS USA app has it all. Dive into live coverage, expert insights, breaking news, exclusive videos, and more. Plus, stay updated on NFL, NBA and all other big sports stories as well as the latest in current affairs and entertainment. Download now for all-access coverage, right at your fingertips – anytime, anywhere.

And there’s more: check out our TikTok and Instagram reels for bite-sized visual takes on all the biggest soccer news and insights.