Explore an Underground Lake in a Glass-Bottom Boat in This Tennessee Town

Sweetwater, Tennessee is home to The Lost Sea, America’s largest underground lake.

You've probably heard of the Dead Sea, the Arabian Sea, and the Mediterranean Sea. They may even be on your travel bucket list, but have you ever heard of The Lost Sea? The Lost Sea, located in the eastern Tennessee town of Sweetwater, is America's largest underground lake, and it's open to visitors year-round.

The Lost Sea is part of Craighead Caverns, a massive network of caves that runs from Sweetwater all the way to the neighboring town of Madisonville. The huge cavern system has quite the history and has been used by animals and humans for thousands of years.

The Lost Sea
Trey Sullins / Courtesy of The Lost Sea Adventure

The cave's first-known human residents were the Cherokees who entered the cave from a tiny natural opening on the side of the mountain. In a large room about one mile from the cave's entrance, artifacts including pottery, arrowheads, weapons, and jewelry were found, proving that Native Americans once used the caves.

Though the caves have been used for years, the Lost Sea wasn't discovered until 1905, when a 13-year-old boy named Ben Sands was exploring the caves and found himself in a room half-filled with water.

Today, visitors can see what young Ben first discovered more than 100 years ago on a tour of the caves through The Lost Sea Adventure. The company operates tours every day of the year, minus Thanksgiving and Christmas Day, from 9 a.m. to anywhere between 5 p.m. and 8 p.m. Note: Tours are temporarily closed through March 2023 for construction and maintenance.

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The guided tour starts with a three-quarter-mile walk on sloping pathways through the caves. While walking, you'll learn all about about the history and science behind the caves. When you've descended 140 feet into the cave, you'll reach The Lost Sea. From there, you'll continue the tour via a boat outfitted with a glass insert on the bottom, so you can peer into the depths that lie beneath. The visible portion of the lake is 800 feet long and 220 feet wide, spanning more than four acres. However, divers have mapped more than 13 acres of water, and there's still more to be discovered.

While on the boat, look out for rainbow trout swimming below and magnificent crystal formations called anthodites overhead. Also known as cave flowers, these naturally occurring formations are composed of long needle-like crystals that radiate from a common base and are only found in a few caves around the world.

Who knew we had such an amazing natural wonder right in our own backyard? At just $24.95 for adults and $14.95 for children, this is one adventure you can't miss.

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