Craighead Caverns is an extensive cave system located in Sweetwater, Tennessee. It is best known for containing the United States' largest and the world's second largest non-subglacial underground lake, The Lost Sea. In addition to the lake, the caverns contain an abundance of crystal clusters called anthodites, stalactites, stalagmites and a waterfall.
The lake was discovered in 1905 by a thirteen-year-old boy named Ben Sands. As the story goes Sands, who often played in the cave, happened upon a small opening and crawled through. The room was so large he was unable to see the ends of the room with his lantern, so he threw balls of mud in all directions and heard splashes. When he went back home and told people of his discovery they were hesitant to believe him. By the time Ben convinced his father to go back down with him to explore it further, the water level had risen, hiding the cave entrance from them. It was rediscovered by local explorers several years later.
The visible surface of the lake measures 800 feet long and 220 feet wide (4.5 acres) at normal "full" capacity. Cave divers have explored several rooms that are completely filled with water, without reaching the end of the cave. This exploration was conducted in the 1970s.
For many years The Lost Sea was considered the world's largest underground lake and is still recognized as the world's second largest non-subglacial underground lake after Dragon's Breath Cave, Namibia.
Boat tours of the lake are still given and for many people are the highlight of the tour. In times of extreme drought (such as 2007-08) the lake recedes significantly and the management had to extend the walkway and the boat dock in order to be able to provide the boat tours. According to the management of the Lost Sea, the water level in the lake dropped 28 feet below its normal level at the height of the drought. At such times visitors see a much larger cavern above the lake surface.
There are also Rainbow Trout in the lake. They aren't native to the Lost Sea, but were added to the lake decades ago in an attempt to see how big the lake was. (It didn't work.) The tour guide has fish food which is thrown to the trout as part of the tour with the glass bottom boat. These fish have also lost much of their color from being in a cave for so long.
