The World's Coolest Caves

The largest trove of Chinese Buddhist art isn’t in Beijing or Shanghai. It’s buried within 492 caves dug by wandering monks along a desert cliff face on an isolated stretch of the ancient Silk Road near Dunhuang. The monks decorated these cave temples with 2,000-plus multicolored sculptures and intricate paintings that could cover more than 11 acres.

Paintings from the fourth to the 14th centuries give insights into evolving patterns of daily life more than 1,000 years ago—and beat your average museum visit any day.

Quarter-inch-long bioluminescent glowworms that radiate a tiny blue light dangle from the ceiling of these caves deep in the lush, subtropical hills of New Zealand’s North Island. Visitors ride in an inflatable raft along the underground Waitomo River with Spellbound Glowworm & Cave Tours. Slowly adjusting to the darkness, they admire what looks like a turquoise starscape.

Glowworms, which dangle sticky, filamentous “fishing lines” to catch insects, are scattered throughout many other caves, but their densely concentrated numbers here make this grotto unique in the world.

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Translucent grayish-white selenite crystal columns, some up to 36 feet long, shimmer in a chamber called Crystal Cave of Giants, 1,000 feet underground in the Naica Mine near Chihuahua. Crystal obelisks several feet wide sparkle in a professional caver’s lights, but temperatures up to 136 degrees with more than 90 percent humidity make visiting extremely dangerous even for the few researchers allowed in.

Nothing remotely like these gigantic crystals exists anywhere else, not even in nearby caves. And the Cave of Crystals was discovered only by chance in 2000 when miners pumped water out of the first 30-by-90-foot chamber.

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In the 13th century, Anasazi or Ancestral Puebloans built 130 rooms and eight ceremonial chambers (kivas) in this 216-feet-long and 89-feet-deep cliff dwelling. Groups of 60 to 80 people lived here and farmed corn, beans, and squash.

It’s the best-preserved Anasazi cliff dwelling—90 percent is original—and, 700 years later, you can still see plaster paintings of birds and mountain sheep.

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It wasn’t until 2009 that professional cavers explored the world’s largest cave passage, which stretches for two-and-a-half miles and reaches 300 feet wide and more than 600 feet high. It’s concealed under dense tropical rainforest in Phong Nha-Ke Bang National Park. It may be quiet aboveground, but below, the Rao Thuong River roars through the cave, echoing off its limestone walls.

In several places the cave ceiling collapsed, leaving skylights 100-plus feet in diameter that let sunlight in. Underneath those skylights, jungle environments with their own ecosystems, including fish and insects, evolved.

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Sure, these caverns have pink and peach and rose-colored stalagmites and stalactites by the hundreds, but keep your eyes peeled for the rare helictites. These delicate calcite formations grow out from the walls and twist and turn in all directions; they line the Crystal Palace as well as the Christmas Tree Room, Valley of Ice, White Moon Falls, and Palace of the Angels.

Geologic features develop especially slowly here, making the oddly shaped formations more translucent than in most caves.

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A small hot-springs cavern was enlarged to create a 150-foot-long H-shaped cave filled waist-high with mineral water as hot as 108 degrees. The odorless water naturally drips from the ceiling and down the walls, building stalactites and smooth “flowstone” that’s been colored red, orange, blue, and green by the minerals.

Hot springs in a cave are unusual, but those who really want “cool” can brave the outdoor stream-fed, cold plunge pool that overlooks Kootenay Lake and the Purcell Mountains.

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Ice Age artists near Rouffignac in southwestern France created detailed line drawings and fine engravings of 158 mammoths, still visible on these walls. Sixty-five animals, including ibex, horses, bison, and rhinoceroses, circle the Grand Ceiling. While Paleolithic artists who painted cave walls and ceilings often had to crawl on their bellies through low passages, modern-day visitors can arrive in style: an electric train makes the half-a-mile trip into the hillside.

The “bearded anthropomorphic figure” is one of the few human likenesses in Ice Age caves.

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One look at the red, orange, and green rocks, lichen, and algae, and it’s easy to see how this sea cave—one of the largest and deepest in the world—got its name. The most frequent visitors are brown pelicans, shearwaters, oystercatchers, Xantus’s murrelets, harbor seals, and sea lions, whose barks resound off the cavernous walls.

Kayak tours with trained naturalists take travelers through the caves, exploring the area's wildlife, geology, and natural and cultural histories.

An ethereal turquoise world greets divers as they float past underwater stalactites and stalagmites illuminated by dramatic shafts of sunlight. Part of the third-largest underwater cave system in the world, the Dos Ojos or “Two Eyes” cenote is two sinkhole entrances to crystal-clear, freshwater-filled caverns in the Yucatán, where cracks in the limestone landscape created a network of caves and sinkholes.

Both “Ojos” are well suited to snorkelers. If you have an open-water certificate (or equivalent), you can dive with a guide from Dos Ojos Scuba Shop (groups of four maximum).

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Among in the remote glacial waters of General Carrera Lake—the second largest freshwater lake in South America—lies a jaw-dropping 5,000 million tons of marble. The Cuevas de Marmol, which also goes by the moniker Marble Cathedral, was naturally formed by more than 6,000 years of waves crashing against calcium-carbonate. To say it’s located a little off the beaten path would be an understatement (it takes flying 800 miles from Santiago to the city of Coyhaique followed by a 200-mile drive into the wilderness and a boat ride just to get there), but once faced with the spectacular turquoise light show on the pristine marble columns, you’ll forget all about the long-haul journey.

In case you’re wondering what makes the white marble appear that stunning blue hue, it’s the reflection from the azure waters. Depending on water level and season, the chameleon-like cave is known to change colors. In the spring, expect shallow, turquoise waters that create a shimmer against the walls, while summer brings an intense blue shade due to a greater depth. No matter the time of year, though, the magical tunnels are sure to mesmerize.

Tucked in the Guangxi Province, this natural limestone labyrinth has been attracting tourists for more than 1,200 years. Aptly named for the reeds growing outside that can be fashioned into flutes, the 787-foot long water-eroded cave is lined with an impressive collection of stalagmites and stalactites. Mix in colorful neon lights that illuminate the peculiar-shaped rock formations and you’ve got a surreal, dream-like experience.

If the neon light spectacle wasn’t enough wow-factor, the ink inscriptions, which allegedly date back to the 792 AD during the Tang Dynasty, should seal the deal.

Known to the Celts as Uamh-Binn (or “The Cave of Melody”), this cavernous wonder was named Fingal’s Cave after Irish folklore by naturalist Sir Joseph Banks who visited the site in 1772. Today, stepping inside the 72-foot tall, 277-foot deep space is a lot like walking through a fantastical movie set. Located on the island of Staffa, the highlights here are the hexagonal, Lego-like columns of basalt (similar to those of Ireland’s Giant’s Causeway), a naturally arched roof, and ominous echoes made by the waves.

Legend has it the geological site has impacted all kinds of artists, including composer Felix Mendelssohn, who used the location as inspiration for his Hebrides Overture, and Pink Floyd, who named one of their early unreleased tracks after the cave.

Beneath the 80-square mile surface of Kentucky’s Mammoth Cave National Park sits the longest cave system in the world. With more than 400 miles of the network already explored, no one knows how far the limestone caves extend in actuality. And since the first person descended over 4,000 years ago, new caves are continually being uncovered. Now, does that name make sense?

Drawing in hundreds of thousands of tourists each year, the caverns are packed with brilliant stalactite formations that were naturally formed from years of water dripping through the cave’s limestone roof.

Located in Gunung Mulu National Park on the island of Borneo, the Mulu Caves house some of the world’s largest cave chambers and systems. The Sarawak Chamber, which can hold 40 Boeing 747 planes, comes in at almost 2,000 feet long and over 260 feet high. Then there’s the Deer Cave, which is 174 meters wide and 122 meters high in one section. Here, look out for the rock formation that resembles Abe Lincoln’s profile.

Every day around dusk, millions of resident bats fly out of the caves in a swirling pattern in search of food, offering tourists a feast for the eyes.