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Found all over the world in a variety of climates and ecosystems, caves are large underground openings in the earth that form from melting ice, volcanic activity, or erosion over hundreds of thousands of years. Full of rock formations, stalactites, stalagmites, and even glaciers, these global treasures are sought-after attractions for explorers looking to experience natural beauty unlike anywhere else on the planet. Ready for a spelunking adventure? Here are 15 of the coolest caves in the U.S.
Jewel Cave (Custer County, South Dakota)
Named after the crystals that cover its walls, Jewel Cave is the world’s third longest cave. In addition to the crystals, which are actually nailhead spar and dogtooth spar, Jewel Cave features unusual formations like cave popcorn (named for its resemblance to popcorn), ribbonlike draping called cave bacon, boxwork, and flowstone, formed from thin layers of calcite. Located beneath South Dakota’s Black Hills, Jewel Cave is filled with small crawl ways, rooms of boulders, tiny silver hydromagnesite balloons, and 30-foot-long ceiling draperies formed from running water.
Luray Caverns (Luray, Virginia)
Luray Caverns are the largest caverns in the eastern United States, home to cathedral-sized rooms with towering rock formations. Standout features include the picturesque Great Fallen Stalactite, the Great Stalacpipe Organ (a lithophone that can be heard from any place inside of the Caverns’ 64 acres), and the Dream Lake, famous for the beautiful optical illusion caused by its reflection. There’s also Pluto’s Ghost, a soaring rock structure named for its pale color caused by pure calcium carbonate, and the Wishing Well, popular for coin-tossing.
Moaning Cavern (Vallecito, California)
Originally named for the unique vocal sound that it emitted, the so-called Moaning Cavern doesn’t moan anymore, ever since it was adapted for tourists. Located in Calaveras County in California’s Gold Country, Moaning Cavern provides a quick education in both the history and topography of California. The cavern was used as a burial ground for the Miwok Tribe, and remains from human beings living over 12,000 years ago have been found within its walls. Today, tourists can visit the Moaning Cavern for casual sightseeing using its famous 100-foot spiral staircase or get on their hands and knees to do some intense spelunking through its most challenging passages, with names like “Birth Canal” and “Santa’s Worst Nightmare.”
Carlsbad Caverns (Eddy County, New Mexico)
Carlsbad Caverns National Park in New Mexico’s Chihuahuan Desert contains more than 119 limestone caves to explore. The most popular route, the Big Room Trail, is a grand 1.25-mile path that winds throughout the caverns and showcases formations like the Hall of Giants, the Bottomless Pit, and the Chandelier. There’s also the Natural Entrance Trail, where explorers can descend from the outside world into the dark of the Big Room, which is North America’s largest single cave chamber. Visitors can also watch thousands of bats that live inside the caverns emerge and take their nightly flight.
Niagara Cave (Fillmore County, Minnesota)
This cave boasts an underground 60-foot waterfall, 100-foot-high ceilings, 450-million-year-old fossils, an echo chamber, and even an underground wedding chapel. In 2015, Niagara Cave also became the world’s first commercial cave to have its energy use 100% offset by solar energy. Inside, the cave’s temperature remains at 48 degrees Fahrenheit year round. According to legend, the cave was first discovered in 1924, when a farmer went searching for his three missing pigs — only to discover them 75 feet underground, in the chamber now known as Niagara Cave.
Cosmic Cavern (Berryville, Arkansas)
North Arkansas’ Cosmic Cavern is the warmest cave in the Ozarks at a balmy 62 degrees Fahrenheit. Along with breathtaking formations — flowstone, cave popcorn, cave bacon, soda straws, and helictites — the cosmic caverns are also home to two lakes that are technically “bottomless,” as divers and researchers have not been able to reach the lake floors.
Meramec Caverns (Stanton, Missouri)
Missouri’s state nickname is the Cave State, and for good reason — it’s home to more than 6,000 known caves. One of the most visited is Meramec Caverns, which sprawl through 4.6 miles of underground terrain in the Ozarks. Featuring numerous attractions and themed caves, Meramec Caverns are among the must-see stops along Route 66. They are also steeped in the history of the region, as it's rumored that outlaw Jesse James used the caves as a hideout, and segments of Tom Sawyer and Lassie were filmed there.
Mendenhall Ice Caves (Juneau, Alaska)
Only 12 miles from the capital city of Juneau, Alaska, lies the stunning blue-walled wonder of the Mendenhall Ice Caves. Situated within the 17-million-acre Tongass National Forest, the Ice Caves are accessible only by kayak but well worth the effort. The caves lie within a partially hollowed glacier, so you can stare up into the brilliant blue of the ice and water above while standing in the cave below. Consider visiting soon, however, as climate change is threatening a rapid retreat of the glacier.
Marengo Cave (Marengo, Indiana)
Located in the Blue River Basin of Southern Indiana, the Marengo Cave is part of what is known as a “karst region,” defined by the erosion of underlying limestone and other soluble rocks by acidic water. This erosion leaves behind a complex drainage system that features sinkholes, disappearing streams, and caves. Marengo Cave is the spectacular result of this geological phenomenon, featuring myriad different formations, rare species of animals, and unique karst habitats like limestone glades, chert barrens, and upland sinkhole swamps.
Craighead Caverns (Monroe County, Tennessee)
Buried in the foothills of the Great Smoky Mountains in southeastern Tennessee, the Craighead Caverns have a rich history and even richer natural landscape. Over the past few centuries, the caverns have played host to Native Americans, Confederate soldiers, a mushroom farm, and a bar called the “cavern tavern.” The caverns feature crystal deposits, a waterfall, and the so-called “Lost Sea”, a surreal subglacial lake that is now considered to be the second largest of its kind in the world.
Oregon Caves (Josephine County, Oregon)
Home of the famous “River Styx,” a subterranean river named after the river to the Underworld in Greek mythology, the Oregon Caves are situated in the Klamath Mountains of southwestern Oregon. Featuring a marble cave and other captivating cave formations, the Oregon Caves have been designated as a National Historic Landmark since 1933. The caves offer myriad options for cave exploration, including an advanced “off-trail” cave exploration that has guests squeeze through spaces as narrow as 11 inches by 19 inches.
Glenwood Caverns (Glenwood Springs, Colorado)
Formed by naturally occurring hot springs, these expansive caves span more than 10 miles beneath Iron Mountain in Glenwood Caverns Adventure Park. The Glenwood Caverns offer both entry-level tours like the Fairy Cave for the cave-curious and advanced cave exploration in their Wild Cave for more experienced spelunkers. Bring a jacket, as the caves are always precisely 52 degrees Fahrenheit. Across the Colorado River, you can take a dip in one of the hot springs that formed the Glenwood Caverns in the Iron Mountain Hot Springs.
Ellison’s Cave (Walker County, Georgia)
Ellison’s Cave is the 12th deepest cave in the U.S., with a total vertical descent of 1,063 feet and a length of 12 miles. It is known best for its underground pits, including Fantastic Pit, Incredible Pit, and the Warm Up Pit, which create a labyrinth of routes and passages throughout the cave system. The Fantastic Pit is the deepest cave drop in the continental U.S. — at 586 feet, it’s twice the height of the Statue of Liberty. Due to the incredible depth of this cave, it isn’t recommended for beginners;visitors to Ellison’s Cave should have extensive experience with vertical caving and rope-climbing.
Caverns of Sonora (Sonora, Texas)
These caves are known for their unusual and spectacular translucent mineral deposits called speleothems, as well as for the Crystal Palace, composed of beautiful calcite formations that resemble crystals. The cave was likely formed between 1 million and 1.5 million years ago. Visitors can repel 43 feet into Sonora’s “Devil’s Pit,” or try “off-trail” caving.
Mammoth Cave (Central Kentucky)
This Kentucky cave system is the longest known cave system in the entire world, with more than 400 miles of caves and passages and 130 species of wildlife. It’s the centerpiece of Mammoth Cave National Park, a 53,000-acre park that also includes sprawling river valleys and forests. Visitors can take candlelit tours, crawling tours of undeveloped passages, and historic tours to learn about the cave formations, some of which were formed 3.2 million years ago.