With an estimated 45,000 caves within the contiguous United States, there's a whole world to explore beneath the surface, from the "Cave State" of Missouri to Carlsbad Caverns in New Mexico.

Whether spelunking your way through less-developed caves or participating in a guided tour past stalactites and stalagmites, these caves and caverns will take you on subterranean adventures beneath America.

1. Jewel Cave -- Custer, South Dakota


BCK7H7 The Formation Room, Jewel Cave National Monument, South Dakota. Image shot 2009. Exact date unknown. (Clint Farlinger/Alamy)

With more than 170 miles of explored passageways, this cave ranks third longest in the world. Since 1908 Jewel Cave has been designated a national monument. The year-round Wild Caving Tour ($31 for adults, no children under 16) is one of three guided tours offered. It takes you on a three-to-four-hour adventure that will have you scaling rocks via ropes and crawling your way through nearly a mile of this massive unground system. While touring you'll also peer into ominous fissures, pass giant boulders, and spot strands of gypsum in the presence of the nine bat species that call the cave home during the winter months.

2. Carlsbad Caverns -- Carlsbad Caverns National Park, New Mexico


(Photo courtesy Peter Jones / NPS)

The 119-odd caves that make up this national park are home to some 400,000 bats, countless fossils from pre-Jurassic times, ​and scientists believe one of the caves may contain microbes that could be used in a cure for cancer.​ General admission ($10 for adults, free for children) grants you access to two self-guided tours through Carlsbad Caverns via an elevator and lit walkways. The tour includes the aptly named Big Room, the largest in the cavern at 357,480 square feet. For an additional fee, you can rent a headlamp and play speleologist (professional cave-studier) on guided tours through ​additional parts of the cavern.

The Mexican free-tailed bats that call these caverns home put on quite the show. Between May and October, you can watch as they come barreling out of the cave and take flight for ​the night​. Catch the ​show around sunset at the outdoor Bat Flight Amphitheater​ (free with park admission) ​near the park's entrance.

3. Luray Caverns -- Luray, Virgina


(Photo courtesy Luray Caverns)

This cavern is home to some impressive rock formations, among them a large leaning column and with a rock formation that resembles folded ribbons. But the real gem of Luray Cavern is the aptly named Great Stalacpipe Organ. It claims to be the biggest instrument in the world and uses electronically-controlled rubber mallets to gently tap the cave's stalactites, turning three acres of the cave into a lithophone and performance space.

Luray Caverns is open every day of the year and costs $26 for adults and $14 for children ages six to 12. Admission includes a guided-tour of the caverns, and entrance into the nearby Car and Carriage Caravan and the Luray Valley Museum.

4. Wind Cave -- Hot Springs, South Dakota​


(Photo courtesy NPS)

This cave has no shortage of bragging rights: It's considered the densest cave system in the world and houses nearly all (95 percent) of the world's boxwork formations, a​n​​ intricate​ calcite formation that ​resembles a honeycomb or spiderweb and covers surfaces in the cave.​ Wind Cave was designated a national park in 1903, making it the first cave in the world​ to earn the status. ​

​You can explore the cave on a number of National Park Service-led tours, including ​the Historic Candlelight Cave Tour ($12 for adults, $6 for children). Those looking for more of an adventure will enjoy the Wild Cave Tour ($30, ages 16 and up only), which will have you crawling your way through much of the cave's less developed areas.

5. Meramec Caverns -- Sullivan, Missouri


(imageBROKER / Alamy)

Drive through the Cave State and visit Meramec Caverns. Located along historic Route 66, this popular attraction had several claims to fame before it even opened to the public in the 1930s, including being used as a hideout for infamous outlaw Jesse James and his gang and serving as one of the last stops on the Underground Railroad.

Like many roadside oddities and attractions along Route 66, the caves are a tad kitschy, but that's half the fun. Go in expecting to see 400-million-year-old rock formations that will leave you in awe, but know that some of them are adorned with neon lights and stand next to manmade props. ​The more than caverns can be toured independently or with a park ranger. Admission is $21​ for ​adults and ​$11 ​​for children ages five to 11.

Check out more amazing U.S. caves.

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