The Most Incredible Things Discovered In Caves

This wide, wonderful, weird world called Earth is filled with all kinds of ridiculously cool things: All it takes is a healthy curiosity about the world around us, and there's no limit to the number of things out there waiting to be discovered.

When it comes to the planet's landscape, there's one thing that's undeniable: Caves are cool. It's impossible to see a cave and not wonder what's inside, because even though the answer is usually something like "rocks" and possibly "bears," there's something about these things that just capture the imagination. There's good reason for that, too — sometimes, there have been incredible, unbelievable things discovered in caves.

Sometimes, that includes finding things like more caves. In 2021, the Cave Research Foundation announced (via the National Park Service) that they had found more miles of tunnels that were a part of the Mammoth Cave National Park. It was already the longest cave in the world, and with the newly discovered tunnels, it hit a length of 420 miles. For some perspective, that means driving the length of the caves would be like driving from New York City to Norfolk, Virginia. That's pretty wild, but when it comes to the most incredible finds in the history of caving, that's not even scratching the surface.

Caves, says How Stuff Works, have different ecological zones. At the entrance is the aptly-named entrance zone (which gets lots of light), past that is the twilight zone (which gets a little light), and beyond that is the dark zone, where there is no light and only life that's adapted to live in a black void of nothingness. And it's in the dark zone of a cave just outside of Knoxville, Tennessee that a group of cavers discovered the first ancient cave art in North America.

According to Jan Simek, professor of anthropology at the University of Tennessee (via The Conversation), the group of amateur cavers was the first to lay eyes on the drawings of animals, birds, humans, and half-animal, half-human creatures in about 800 years. The art found in what became known as Mud Glyph Cave was ultimately linked to the Mississippian people, and what followed was further investigation and the discovery of 92 more sites across the American southeast (as of 2021). And strangely? They're all connected.

Simek later told CNN that the artwork was found to be from 6,000 to 500 years old, and it was only after documenting and compiling all the artwork that they realized it was all connected: It was all depicting a cosmology of an upper world, the so-called middle world — where plants, animals, and people lived — and a world that included the caves themselves, which "were places ... boundaries could be crossed."

Archaeologists had first started exploring and documenting Bruniquel Cave in the 1990s, but it wasn't until 2016 that National Geographic reported on the findings in a single chamber, around 1,000 feet from the cave's entrance. It was there that archaeologists found a series of rings, constructed from almost 400 stalagmites (weighing a total of about 2 tons), cut to the same height and carefully arranged. In addition to one large circle that's about 22 feet in diameter, there was also a smaller semi-circle of stalagmites, with the remaining stalagmites stacked in several seemingly meaningful, central piles. While some naysayers think it's a weird coincidence that can be explained away by the behavior of hibernating bears, that, most say, is doubtful — particularly because they've also found traces that fires had been lit and burned among the circle, and bones had also been burnt at some time.

And it's the time frame we're talking about here that's really cool, because as much as it looks like the sort of thing early — but modern — humans would build, it predates Homo sapiens by a lot. The site has been radiocarbon dated to 176,000 years ago, which means that it was Neanderthals who not only organized the construction of these clearly meaningful patterns — and lit the deep cave while they were doing it.

It could change the way we think of Neanderthals: As study co-author Jacques Jaubert of the University of Bordeaux explained: "All this indicates a structured society."

Geologist Juan Manuel Garcia-Ruiz says (via National Geographic) that the Cueva de los Cristales — or, Cave of Crystals — is "the Sistine Chapel of crystals," and that just might be an understatement.

In 2000, miners excavating a new tunnel found something unbelievable, tucked away in a cave 1,000 feet below Peru's Chihuahuan Desert and the Naica mountain: When they broke into the cavern, they found it was filled with some of the world's largest crystals, measuring up to 36 feet in length and weighing as much as 55 tons. (For some reference, that's about equal to the weight of nine elephants.)

Since then, there's been quite a bit of research done in the caverns — which is difficult, because according to the BBC, there's nearly 100% humidity inside, and the air is so hot that it's cooled as it enters the lungs. Geologists have discovered that the whole thing started forming about 26 million years ago, with help from some serious volcanic activity. The crystals themselves have been growing for hundreds of thousands of years, and now, there's a more pressing question than, "How were they formed?" That, says C&EN, is the question of how to protect them. Although the cave's natural state was perfect for the formation of these massive crystals, mining activities in the area have changed that environment, and they're at risk of dehydration and destruction.

On one June afternoon in 1836, a group of boys was exploring an area known as Arthur's Seat in Scotland — and they just happened to stumble across what's become one of the nation's weirdest mysteries. According to National Museums Scotland, the boys had stumbled across a little cave while on their adventures. The entrance to the cave had been blocked with a few pieces of slate, and when they looked inside, they found 17 miniature coffins, complete with figures that had been neatly dressed in little handmade clothes, then nestled inside the coffins. Yikes.

At the time, newspapers picked up on the find and started screaming about witchcraft, demonology, and black magic, because of course they did. Others suggested less outlandish explanations, like the possibility they were effigies representing friends who had died in faraway lands or had been lost at sea, and the dolls had been given proper rites in their place. That's actually pretty sweet, but the current theory isn't nearly as heartwarming.

It's now thought that the 17 coffins had been made — and buried — as a tribute to the 17 victims of notorious bodysnatchers William Burke and William Hare. They got their start when a fellow boarder at the house Hare was staying at had the misfortune of dying while owing him money, so they collected by selling him to a local anatomy school. Who made them? Why? Was it really a tribute to Burke and Hare's victims? It's unlikely we'll ever know.

The Kabayan Mummy Burial Caves of the Philippines are now recognized by UNESCO for their cultural significance, and it's safe to say that for those who buried their loved ones there, it meant even more than UNESCO can hope to communicate. According to the World Monuments Fund, the caves were used by the Ibaloi tribe, who practiced a form of embalming that was similar to what was found in ancient Egypt. Those who knew that their time on earth was limited would start the mummification process by drinking a salty concoction, and the process would then be completed over the weeks following the death. Once completed, the body would then be interred in decorative wooden coffins and placed in the ancient burial caves — where they were (relatively) recently rediscovered by loggers.

The ancient practices had come to an end with the arrival of 16th-century Europeans, and the mummies had endured for a long time. Once the caves were opened, it introduced all kinds of problems. From bugs and fungus to people being, well, people, it very quickly became necessary to protect the caves — while they're no longer used, the Ibaloi still consider them sacred.

The mummies have been extensively studied since the discovery of the caves, and some — like the chieftain Apo Annu — have been reinterred there. There's a really neat footnote to this, too: According to Archaeology, the study of the exquisite tattoos found on many of the mummies has allowed modern-day descendants to recreate their ancestors' tattoos.

No one's easily getting to Scotland's Sculptor's Cave, and even if they do get there, the clock is ticking. Located in the sandstone sea cliffs of Moray, the cave is only accessible during low tide. Archaeologists have now made a full, 3D model of the cave to study from the safety of somewhere else — and it's a fascinating place, says LiveScience. It was first discovered in the 1920s, and according to Canterbury Christ Church University, archaeologists have unlocked more of the cave's secrets.

It's one of the few places where traces of Scotland's prehistoric dead have been found, and it was first used sometime around 1000 BC. That, says the University of Bradford's Ian Armit (via LiveScience), is when prehistoric people were practicing "excarnation, or exposure burial": The bodies were left to the elements, where they would slowly decompose and decay — and there were signs that all the while, the living would come to visit.

In addition to some of the bones bearing marks that seem to indicate they were defleshed and polished, there was also a plethora of Pictish carvings, and a site for visitors to cook while checking on their ancestors. The site was in use for around 1500 years, and things only came to an end in the 4th century AD. That was a little after one of the most surprising finds: In the 3rd century, the cave was the site of the execution and decapitation of at least nine people.

Romania's Movile Cave has been isolated from the rest of the world for 5.5 million years. The Digital Journal notes that's about the same time our ancient ancestors were just sort of starting to think about evolving into humans, and it's also when the cave was sealed by a falling piece of limestone. When researchers popped the top in the 21st century, they found a world that had evolved completely independently.

Discovered in 1986, the cave is only accessible via a long shaft, then a series of limestone tunnels. While it's a relatively pleasant 77 degrees Fahrenheit, it smells like rotten eggs thanks to a pool of sulphuric water at the bottom — which spews hydrogen sulfide when anything breaks the surface. That means it's incredibly deadly, and spending more than a few hours there would lead to massive organ failure.

The life that's evolved there is just as weird. One of the basic building blocks is a type of chemosynthetic bacteria that exists on carbon the way life on the surface needs oxygen. (And yes, scientists are hoping that if they can learn more about these life forms, they might get some ideas on how to deal with various greenhouse gases.) LiveScience says that more than 50 unique species have been discovered, and most are the creepy-crawly sort. In addition to cave leeches, snails, scorpions, and spiders, there's also the "king of the cave," a venomous centipede that is only about two inches long, but is so deadly it's the cave's apex predator.