From the cliffside path that leads down to the sea, about four kilometers away, I come to a halt. This is the spot: a cave, its entrance barely visible. I look up at the looming face of the rock. I sense it staring back at me, beckoning with its stash: hundreds of caves, built over the centuries from the lava flows of Mount Teide. Any one of them could be the cave we’re looking for—here, history has not yet been written.

Within this gorge in southern Tenerife, the largest of Spain’s Canary Islands, a stunning cave was found in 1764 by Spanish regent and infantry captain Luis Román. A contemporary local priest and writer described the find in a book on the history of the islands: “A wonderful pantheon has just been discovered,” José Viera y Clavijo wrote. “So full of mummies that no less than a thousand were counted.” And thus the tale of the thousand mummies was born. (Read about the different types of mummies found worldwide.)

Few things are more exciting than navigating the ambiguous edge between history and legend. Now, two and a half centuries later, in the gorge known as Barranco de Herques—also called “ravine of the dead” for its funerary caves—we find ourselves in the place that most local archaeologists consider to be the mythical “cave of the thousand mummies.” There are no written coordinates; its location has been passed on by word of mouth among a chosen few. The hikers who venture along the path are oblivious to its existence.

In the company of islander friends, I feel privileged to be shown the place where they believe their ancestors once rested. I crouch toward the narrow opening, turn on my headlamp and drop to the ground. To find this hidden realm, we crawl in on our stomachs for a few claustrophobic meters. But there’s a reward for subjecting ourselves to the tight squeeze: a tall, spacious chamber suddenly opens before me, holding the promise of a journey to the island’s past.

“As archaeologists we assume that the expression ‘thousand mummies’ was probably an exaggeration, a way to suggest that there were indeed a lot, a whole lot—hundreds,” says Mila Álvarez Sosa, a local historian and Egyptologist. In the darkness, our eyes slowly adjust. We survey the space for the telltale signs of a necropolis in the meandering lava tube, part of an extensive system across the island.

These weren’t the first mummies to be unearthed on the island. But according to local lore, a large sepulchral cave like this one held the pantheon of the nine Mencey kings who ruled the islands in precolonial times.

But the most remarkable finding was hidden: unlike its Egyptian counterpart, the Guanche mummy had not been eviscerated. Its organs, including the brain, were perfectly intact thanks to a mixture—minerals, aromatic herbs, bark of pine and heather, and resin from its native dragon tree—that halted bacteria and thus decay, inside and out. Radiocarbon dating in 2016 revealed a tall, healthy male, perhaps a member of the elite, given the condition of his hands, feet, and teeth.