Named "America's Largest Underground Lake," this tourist attraction in Sweetwater, Tennessee also features caves with many unique formations called Craighead Caverns. The Lost Sea was discovered in 1905 by 13-year-old Ben Sands and the cave had been used for storage in the early 1800s by settlers. The caves were opened to the public around 1915. The Lost Sea offers glass-bottom boat rides, tours, a nature trail, eateries and a gem mine. Craighead Caverns is a U.S. National Natural Landmark.
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