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Caves conjure up images of dangling bats dangling, stalagmites and stalagtites rising from floors and ceilings and dark, dank holes that seem to to go on forever.
Here are the seven longest caves of the world, complete with many of those attributes, as well as many hidden gems.
Fisher Ridge CaveSlide 2 of 15
Fisher Ridge Cave
Length: 113 miles (181 kilometers)
Location: Kentucky, USA
The Fisher Ridge Cave System was discovered in January 1981 by a group of Michigan cavers associated with the Detroit Urban Grotto of the National Speleological Society.
It is located near the Mammoth Cave system, and if a connection is found between the two caves in the future, as well as nearby Martin Cave, the total mapped area would exceed 500 miles (804 kilometers).
In addition to the rapid pace of passage discoveries, 113 miles (181 kilometers) in the past 29 years, exciting archaeological finds were discovered in some of the cave's passages. Footprints, cane torch remains, and an interesting scratch mark motif were found. Carbon dating of some of the finds indicates there were visitors to the cave nearly 3,000 years ago.Slide 3 of 15
Holloch CaveSlide 4 of 15
Length: 121 miles (195 kilometers)
Location: Muotha, Switzerland
'Hölloch' translates into English as "Hell's Hole," but the first syllable of the word means "slippery" in the local German dialect.
The initial exploration of the cave started in 1875 and was led by Alois Ulrich. A large part of the exploration of thin in a layer of gypsum less than 66 feet (20 meters) thick.Slide 5 of 15
Lechuguilla CaveSlide 6 of 15
Length: 128 miles (206 kilometers)
Location: New Mexico, USA
Lechuguilla Cave is the deepest limestone cave in the United States, containing formations and microbes found nowhere else in the world.
Small amounts of bat guano were mined from the entrance passages for a year under a mining claim filed in 1914.
The Caves contain large amounts of gypsum and lemon-yellow sulfur deposits. Rare speleothems can be found there as well, including 20-foot (6 meters) gypsum chandeliers, 20-foot (6 meters) gypsum hairs and beards, 15-foot (4.6 meters) soda straws, (speleothems shaped like hollow mineral tube that grow in places where water leaches slowly through cracks in rock)., hydromagnesite balloons (small, gas-filled pouches usually made of hydromagnesite), cave pearls, subaqueous helictites(a speleothem that changes its axis from the vertical to horizontal at one or more stages during its growth.), and rusticles (a formation of rust similar to an icicle or stalactite).Slide 7 of 15
Wind Cave:Slide 8 of 15