World's Coolest Caves

Saalfeld Fairy Grottoes, Germany

Located in the German state of Thuringia, the Saalfeld Fairy Grottoes (or Feengrotten) used to be mined for shale and were largely forgotten after their closure in the mid-19th century. In 1910 they were rediscovered, but far from being a derelict old cave system, the Fairy Grottoes had developed stunning multicolored mineral deposits. Today, the rainbow-hued caves are open to the public, and they're accompanied aboveground by the Feenweltchen village, a family-friendly fantasy experience staffed by people dressed up as fairies and elves. Top off your visit with a stop at the Grottoneum, an interactive museum dedicated to the grottoes' history.

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Hang Sơn Đoòng, Vietnam

Running for more than nine miles, this is the largest single cave in the world. Located in Vietnam and connected to another cave system by its river, there are three ceiling collapses along its length, allowing sunlight to come through and lush vegetation to grow. Sơn Đoòng was created by the river that runs through it, and experts estimate it to be anywhere from two to five million years old. Sơn Đoòng is recommended for intermediate cavers, as its entrance is tricky to traverse. Guided tours are operated exclusively by Oxalis Adventure Tours.

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Shell Grotto, England

Shell Grotto in Margate, Kent, England — Itinerant / Alamy Stock Photo

What could be a better adventure than delving into an underground mystery? Shell Grotto in Margate, Kent, is a subterranean passageway lined with intricate murals made entirely of seashells. Discovered in 1835, experts have been unable to make a definitive estimate of its age, and its purpose also remains a total unknown — though some theories suggest it could be related to the Knights Templar, a prehistoric astronomical society, or some 18th-century rich guy’s hobby. Whatever the reason for its existence, there’s no denying that Shell Grotto is one of the most fascinating and beautiful subterranean wonders to visit.

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Mendenhall Ice Caves, Alaska

Located just outside Juneau, Alaska, the Mendenhall Ice Caves meander through the Mendenhall Glacier, blazing blue and white as sun shines through the ancient ice. Travelers describe them as ethereal, breathtaking, awe-inspiring — you get the idea. Because the Mendenhall Glacier is ever-changing, the caves themselves may not be the same from visit to visit, but that just makes the experience that much more unique. Several outfitters provide guided tours through the Ice Caves and around the surrounding Alaskan landscape, both of which are worth exploring.

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Waitomo Glowworm Caves, New Zealand

The Waitomo Glowworm Caves are home to a species of glowworm found only in New Zealand — and, in fact, they boast the largest and brightest population of the critters that's available for public viewing. With a focus on environmentalism and sustainability, tours here educate travelers on the importance of preservation while bringing visitors on a blackwater rafting adventure they’ll never forget. If rafting isn’t quite your thing, you can also hike through the caves. Before descending, stop at the Waitomo Caves Discovery Centre to learn more about the glowworms and to book tours for all ages and fitness levels.

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Blue Grotto, Italy

Blue Grotto, Capri — Danita Delimont/Getty Images

Capri’s famous sea cave is flooded with stunning blue light, and its long and storied history includes stints as a Roman marine temple and the personal bathing pool of Emperor Tiberius. Though swimming is not allowed today, travelers looking to see the Blue Grotto for themselves can book a sea tour and be rowed inside. The light is best between noon and 2 p.m., and the Grotto is generally closed during the winter to avoid bad weather. After your trip into the cave, you can venture over to the Casa Rossa museum to see the ancient Roman statues that were once displayed inside.

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Fingal’s Cave, Scotland

Fingal’s Cave owes its fame to the naturally formed hexagonal basalt columns that surround the entrance. It’s easy to see how this site has inspired fantasy landscapes, music, and myths aplenty. Travelers can take a guided tour to hike within the cave and see the Isle of Staffa, on which it is located. Get ready for the ultimate karaoke — Fingal’s Cave is legendary for its incredible natural acoustics.

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Škocjan Caves, Slovenia

The special ecosystem within Škocjan Caves (in addition to their breathtaking beauty and massive size) earned them a spot on UNESCO’s list of cultural and natural World Heritage Sites in 1986. Every year, thousands of people flock to the entrance, where the Reka River is swallowed by the caves. These Slovenian caves have been inhabited since the Mesolithic period, and trekking through their chambers feels a bit like going back in time.

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Mammoth Cave, Kentucky

At more than 400 miles long, the interconnected caverns known as Mammoth Cave are the largest cave system in the world. Called “a grand, gloomy, and peculiar place” by early guide Stephen Bishop, the cave is managed today by the National Park Service as Mammoth Cave National Park. It's believed that humans have used and explored Mammoth Cave for as many as seven millennia, and the site has operated as a tourist attraction since the mid-1800s. Tours are offered by the National Park Service, and travelers can stay in nearby lodging to have easy access to the entire park.

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Barton Creek Cave, Belize

Barton Creek Cave may seem small compared to its companions on this list, but what it lacks in size it makes up for in story. As a Mayan ceremonial cave, its rich history is as fascinating as its soaring ceilings. Traveling by canoe, adventurers will see 10 ledges that historians have determined were staging areas for Mayan rituals, including fertility rites and human sacrifice. Part of the cave also served as a burial chamber, with the remains of at least 28 humans having been identified here. This fascinating history makes Barton Creek Cave a true contender for must-see natural wonders.

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Puerto-Princesa Underground River, Philippines

A UNESCO World Heritage Site, the Puerto-Princesa Underground River in Palawan is over 30 million years old. Described as eerie, spine-tingling, and awe-inspiring, the Underground River is traversable by kayak, allowing you to absorb the experience in serenity. While some of the cave is inaccessible due to lack of oxygen, the first mile is open to everyone and another two and a half miles are accessible with a special permit. As you paddle, keep an eye out for the cave’s soaring ceilings (they stretch almost 250 feet high in spots) and the ancient fossils embedded in the walls. The park surrounding the river is well worth exploring, too, with several species of wildlife that can be found only in Palawan.

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