In a remote part of the Philippines, high up a mountain, are some of the world’s most terrifying caves. There’s a reason why only the most intrepid of locals dare to venture inside.

Image: Flickr/Anna Kaminski — Image: Anna Kaminski

Mt. Pulag looms large over Luzon, the biggest of the Philippines’ islands. It’s covered by lush jungles, historic villages and mysterious caves, whose dark secrets have been guarded for millennia. Indeed, had it not been for the loggers who arrived here at the end of the 19th century, they may have been forgotten forever.

Image: Flickr/Anna Kaminski — Image: Anna Kaminski

But pity the first poor logger to stumble upon the caves. If he hadn’t already been unnerved by the “sea of clouds” that envelops Mt. Pulag at dawn, then what he found would certainly have made his blood run cold.

Image: Flickr/karen easterbrook — Image: karen easterbrook

Even modern-day explorers get creeped out by the historical artifacts hidden within. In fact, these days the rock shelters are reached by narrow, twisted paths, with crooked stone steps leading down into their open jaws.

Image: Flickr/karen easterbrook — Image: karen easterbrook

But while the cave complex, located near the town of Kabayan, might look like something from an Indiana Jones movie, it’s very real indeed. And what lies inside is far creepier than anything a Hollywood props department could come up with.

Image: Flickr/karen easterbrook — Image: karen easterbrook

Unlike the loggers who first discovered this creepy curiosity, however, today’s sets of visitors each arrive accompanied by a local guide. But even such chaperones feel scared enough to mutter prayers – for protection, perhaps, or maybe for forgiveness – before venturing inside. This, after all, is the resting place of their ancestors.

Image: Flickr/karen easterbrook — Image: karen easterbrook

Anyone expecting serene catacombs is, then, in for a shock. The mummies here are tiny and curled up; they lie fetus-like in cramped coffins. The creepiest thing, though, is that for these people the mummification process started before they died.

Image: Flickr/karen easterbrook — Image: karen easterbrook

These are the Fire Mummies, which are, owing to the indigenous people who made them, also known as the Ibaloi Mummies. And their pre-death rituals, according to some anthropologists, date as far back as 2000 B.C.

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Thanks to modern-day Ibaloi, as well as historic investigations, we have a better understanding of the preservation processes. It went a little something like this: when nearing the end, the dying drank a particularly salty liquid, which set the wheels of the mummification process in motion.

Image: Flickr/Jeno Ortiz — Image: Jeno Ortiz

After the individuals died, their bodies were washed, placed into a sitting-down pose and positioned above flames. The idea, after all, was to dry the corpse rather than cremate it.

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While this was going on, tribe members blew tobacco smoke into the departed’s mouth. This, it was believed, would help the person’s insides to dry. It was, all told, a process that took weeks to complete.

Once fully mummified, the deceased were curled up, lowered into oval-shaped coffins and left in their final resting place. And while most individuals were buried alone, it was common for families to be laid to rest together.

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When Christian explorers from Spain landed in 1500, however, the practice came to an end. Hence, the caves, and the mummies they contained, were subsequently left untouched for centuries.

Image: Flickr/Anna Kaminski — Image: Anna Kaminski

Indeed, it wasn’t for another 300 years, when the loggers moved in, that the rock shelters gave up their secrets. The lumberjacks’ arrival, though, predated organizations like UNESCO, which meant that not everyone respected them.

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The caves were eventually designated a National Cultural Treasure by the Philippines’ government, but this unfortunately didn’t deter vandals. In fact, some mummies were looted and sold on the black market, and one in particular proved to be a devastating loss.

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Apo Annu is believed to have been a tribal chief, and his decorated mummy was stolen from the caves in the early 1900s. It was eventually returned in 1999, but by this point the Ibaloi had suffered failing harvests, droughts and even earthquakes – proof, some say, of a curse brought about by looting.

Furthermore, while other stolen mummies have also been recovered, several remain unaccounted for. Some were even held to be half human, half deity. Is it within their power to continue haunting Mt. Pulag until they’re put back in their rightful place?

Image: Flickr/Anna Kaminski — Image: Anna Kaminski

Many of today’s natives would rather not take any chances. The Ibaloi, it is understood, now keep the location of as many as 80 mummies a closely guarded secret – just in case they ever attract vandals.

On top of the efforts of native guardians, UNESCO has declared the Kabayan caves a World Heritage Site. The complex has also been listed by the World Monuments Fund.

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Some of the most important caves are, for obvious reasons, now gated. And they each remain sacred to the Ibaloi people, who to this day perform time-honored rituals on the sites where their ancestors rest.

Tourists intrepid enough to travel to this part of the Philippines are requested to book one of the native Ibaloi guides. Not only is their knowledge unrivaled, but the prayers they say before entering may just keep any lingering curses at bay.