Underground caverns are one of the more fascinating wonders of our world. It's easy enough to witness the enormity of mountains looming in the distance (or up close if we're adventurous enough) but there's something so alluring about an entire world existing just under our feet.

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Perhaps it's in the mystery of how these gargantuan caves were formed or the fascination behind why they exist. Or, maybe, it's that hundreds of feet underground, it almost feels as though one is exploring a different planet. Whatever it is that attracts us to these natural works of art, there are definitely some that should be on everyone's bucket list... if we dare venture downward.

10 Mammoth Cave In Kentucky

Since this is the world's largest system of caves, it made sense to have it on our list. Mammoth consists of over 400 miles of underground walkways, all open to visitors to book via the internet. With ten tours to choose from, visitors will be in for a wild trip down and past many structures that can be seen nowhere else.

Additionally, Gothic Avenue is a bonus of a trip downstairs. It's filled with 19th-century monuments that have been left by other visitors. With such a tremendous exploration rate, visitors would be keen to plan an entire day underground.

9 Carlsbad Caverns In New Mexico

New Mexico offers many things, but most tourists don't think of one of those being caves. In the Chihuahuan Desert, visitors will find Carlsbad Caves, an eerie underground cavern that was formed by limestone deposits. What makes this cave so unique is its self-guided tour, on which visitors can see everything from the cave's 750-foot entrance to deep canyons hidden within.

Those interested in a more in-depth (and risky) tour can sign up for guided trails, which will allow them to explore the off-limits areas with an expert. These tours are not for the faint of heart.

8 Ruby Falls In Tennessee

While its name speaks for itself, Ruby Falls is quite the sight to behold. Many things can be found in the U.S., but not many realize that plenty can be found underground, too. Ruby Falls is home to a 145-foot waterfall that resides underground.

Not only is an underground waterfall epic on its own, but this cavern is also home to formations of stalagmites, stalactites, and even full columns. Visitors will be able to view a vast array of classic underground formations while soaking in the vast expanse that is this cave.

7 Luray Caverns In Virginia

Luray Caverns has been open to the public for some time and is perhaps one of the most notable in the south. Visitors will literally be surrounded by formations on every side, and what makes each chamber of this cave so unique is its water flow. Many of the chambers have small pools that actually reflect formations on the ceiling, providing somewhat of an optical illusion.

The tour is quite an easy walk, and along the way, visitors can stop and be wow'ed by the only Stalacpipe organ, which plays on various formations to create sounds similar to an instrumental organ.

6 Niagra Cave In Minnesota

Niagra Cave differs a bit from the others because this cavern is not only an underground tunnel system—it's also a wedding chapel! For those who want to experience something a bit different and unique, it is possible to say "I do" in a cave full of 450-million-year-old fossils. That's not all visitors can do, though.

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For the bravest of the brave, the cave also allows nighttime tours, led by lantern. These need to be booked in advance but offer a unique, natural experience when it comes to underground exploration. This cave also boasts an underground waterfall, making for a truly incredibly visit.

5 Craighead Caverns In Tennessee

Just when you thought you'd seen all you could see as far as underground wonders go, we'd like to introduce Craighead Caverns. Deep inside these chambers lies the country's largest underground lake, something that's quite unusual to see in many of the more dry caves in the U.S.

Visitors will also note several other interesting things on their tours, including a unique species of underground fauna. To top off what's bound to be a magical experience, visitors have the chance to end their guided tour with a glass-bottom boat ride through the cavern's hollowed passageways.

4 Ohio Caverns In West Liberty

Ohio Caverns might not seem like much, but visitors will find themselves walking down into this cave in a bit of a strange way. With an entrance that's actually an enormous sinkhole, those who are brave enough to spend some time underground will be amazed by all the unique formations to be found in this giant hole in the ground.

They're eye-catching and colorful, something many don't expect prior to venturing down. One of the main features of this cave is called the Crystal King, a rather large formation that's totally picture-worthy.

3 Cave Of The Winds In Colorado

Cave of the Winds—not to be confused with the Wind Cave in South Dakota—is most definitely for the adventurer in all of us. This cave not only offers an underground tour that includes the option for an unlit lantern tour, but it also allows visitors to take in the breathtaking landscape that surrounds these caverns.

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Among the Manitou Cliff Dwellings, daredevils will find themselves tempted by the rope-walking course and cliff-diving attraction that many a brave soul has taken a spin on. There's no shortage of adventure in this national park.

2 DeSota Caverns In Alabama

DeSota Caverns is yet another cave adventure that lies deep within a gorgeous landscape. After venturing into the Appalachian foothills, visitors can choose to go on a guided tour of what is now considered the largest collection of onyx-marble speleotherms in the world.

If this wasn't enough allure to spark some excitement, then perhaps the cave's history will win you over. It's believed that these underground tunnels were once home to Copena people, which was an indigenous group native to Alabama. Additionally, the cave is believed to have once housed a speakeasy during the Prohibition.

1 Glenwood Caverns Adventure Park

This cave was first discovered in the 19th century and has since been opened to the public. In addition to a fine exploratory cave, this park also boasts what is now a massive adventure park, filled with heart-stopping rides that any daring individual will love.

After having a guided tour through three popular chambers, all adequately named after the formations they hold, visitors can choose to ride the country's first alpine roller coaster. If soaring high above an altitude that most never dream of isn't enough, there are plenty of other height-themed rides to get the adrenaline pumping.

Sources: vacationidea.com, travelzoo.com

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