Formed over thousands, even millions of years, caverns are hidden natural wonders filled with gravity -defying formations made through the Earth’s constant shifting.  While there are some 55,500-plus caves in the U.S., few have become major tourist attractions. Some are too dangerous for amateurs while the discovery of others has just begun.  But you don’t have to be a professional spelunker to explore the beauty down below.  Here are some of the most noteworthy caverns in the U.S.

1. Carlsbad Caverns, New Mexico



Called the "Grand Canyon with a roof on it," Carlsbad Caverns in the Chihuahuan Desert are one of the world’s deepest, biggest and most decorated caverns ever found. They're most famous for the "Big Cave" and its Big Room—a massive 14 acre space filled with unusual calcium-carbonate cave formations.  Visitors can see the Bottomless Pit, Giant Dome, Rock of Ages and Painted Grotto – formations created when sulfuric acid dissolved the surrounding limestone. Only a part of the cave can be viewed on public tours.  More underground rooms go beyond, for more than 30 miles–and those are the ones that have been explored. The deepest chamber is 1,027 feet below the surface. The Carlsbad Caverns are open every day of the year except Christmas Day.

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2. Mammoth Cave, Kentucky



The  aptly named Mammoth Cave is the world's longest-known cave system with over 285 miles of surveyed cave passageways. If you like the spelunking, this is the place for you. Visitors can explore the vast chambers and complex labyrinths, sometimes climbing up hundreds of stairs and steep hills. The more adventurous types can take "wild" tours where visitors explore muddy crawls and dusty tunnels. Check out Fat Man's Misery--a section that is only 18 inches wide at the hips, which is like walking through a shallow trench, or take a tour lit only with paraffin lamps.

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3. Caverns of Sonora, Texas


(Caverns of Sonora)

Sure, the Caverns of Sonora are big – at 150 ft. deep and 20,000 ft. long.  But the cavern -- formed in 100 million-year-old limestone –is best known for the hundreds of pink and rose-colored stalagmites and stalactites that make it one of the world’s most beautiful caves.  Check out the near-translucent helictites, calcite formations grow from the walls in odd and beautiful formations.  Its most famous, The Butterfly, was vandalized when the top portion of the right wing was broken off and stolen Soda straws, long thin, hallow stalactites that grow up to 4 ft. long are also a main feature –and are extremely fragile.

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4. Luray Caverns, Virginia


(Luray Caverns)

Situated in the Shenandoah Valley, Luray Caverns has cathedral-sized rooms with 10-story-high ceilings filled with towering stone columns formed over millions of years ago by underground rivers and acid-bearing water cutting through the limestone and clay.  Discovered in 1878, the Luray Caverns is the third most-visited cave in the U.S., after Mammoth Cave in Kentucky and Carlsbad Caverns in New Mexico.   Visitors should check out the world's only Stalacpipe Organ which creates haunting music when tapped by rubber-tipped mallets on the stone formations, and the Frozen Fountain a shimmering cascade of calcite, a crystalline form of limestone.

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5. Niagara Cave, Minnesota



The Niagara Cave gets its name because the 60 ft. waterfall inside the cave coined by early explorers to Minnesota after the iconic New York destination. But this cave also boasts of huge stalactites, calcite flowstones and fossils that are over 400 million years old.  Visitors can walk through the notable underground sights as Paul Bunyan's Bed, an echo chamber a 20-ft.-tall limestone island called the Battleship.  But best of all, there is a wedding chapel inside the cave, which has seen over 400 wedding ceremonies performed.

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6. Ellison’s Cave, Georgia


(Alex Schmidberger (Purdue Outing Club))

The Ellison's Cave, located in the northwest Georgia, is notable for its breathtaking depth of 1,063 feet and length of 64,030 feet.  Ellison's is the 12th deepest cave in the U.S., but has two of deepest cave drops in the continental U.S. "Fantastic," drops 586 feet --big enough to hold the Washington Monument, and "Incredible," drops 440 feet.  People have died trying to explore Ellison’s cave and is explored by only the most experienced cavers and spelunkers.

7. Jewel Cave, South Dakota



With just over 157 miles of navigated passageways, Jewel Cave is the third longest known cave system in the world, after Mammoth Cave in Kentucky and Sistema Sac Actun in Mexico.   Ranger-guided tours take visitors through the narrow passageways filled with calcite formations, such as stalactites, stalagmites, flowstone, and frostwork,  It even has a rare  hydromagnesite balloon, which is a translucent mineral bubble made out of magnesium carbonate.  Jewel Cave National Monument is open year-round except Thanksgiving, Christmas Day and New Years Day.

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8. Meramec Caverns, Missouri


(Visit MO)

Meramec Caverns is a 4.6-mile cavern system in the Ozarks that was famously once a hide out of outlaw Jessie James. It’s also the most largest  cave in Missouri, in a state filled with some 6,000 caves—23 of which offer tours.  Along with its natural beauty, its kitsch factor makes Meramec notable.  In attempt to lure tourists,  the owners built billboards at sites inside the cavern system and rented out as ad space.  Also, the caves were featured in Art Linkletter’s TV show “People Are Funny,” where a newlywed couple wound up spending their honeymoon there.  The temperature there rarely rise above 60 degrees Fahrenheit, making it a pretty chilly start to the marriage.

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