In scenes that will probably make you feel physically sick and incredibly claustrophobic, a man who clambered through the 'Hell Hole' cave had the ultimate pay-off when he discovered something quite amazing.
Hell hole is a large and deep pit cave located in California's Wilder Ranch State Park.
But watching people explore it's dark and mysterious caverns certainly isn't for the faint-hearted.
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Two people who are brave enough to take on the cave are Jacob and Calvin Saunders, a nephew and uncle duo who run the YouTube channel, Caveman Hikes.
In a video from two years ago, the pair can be seen writhing through various tight tunnels in Hell Hole - but what they found made the challenge very worthwhile indeed.
In one scene, Jacob can be seen squeezing through an impossibly tight tunnel.
"People say they'll die of claustrophobia, I do too," he says.
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Meanwhile, his uncle tells him: "Stay sideways dude, you're going to get yourself wedged in there. You're at the tight spot there.
"You can't get in a hurry at the tight spots, you just have to take it."
Finally, after squeezing through, the pair come across the 'secret' they had been looking for - a four feet-high, limestone pillar.
"Above me is the last limestone pillar in this cave. In the entire cave, people destroyed everything because it's so open," said Jacob.
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"But through these tight squeezes and narrow passages, it's so far back here, so not known about that this is the only one that remains."
Calvin added: "She remains as a secret treasure for those willing to venture beyond the limits of hell."
You can watch the moment, around 13 minutes in:
The pair have been filming their hikes for over five years, and many of the videos will make you feel anxious just watching.
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Speaking about caving, Jacob told the Guardian in 2022: "When I first went in caves, I was terrified.
"Caves will always surprise me. Is it going to be wet? Is it going to be dry? Is it going to be cold, dirty, muddy, clean?
"Is it going to be, like, pretty or is it going to be super ugly, you know, like a crawly cave that’s all spiky?"
In one video, Calvin rips his clothes to shreds just trying to fit through a tight squeeze.
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"A lot of people ask why we do this and you're never going to get a sufficient answer," he says.
"Why do wake up in the morning? What drives you? What makes you want to get up and study a subject or go to work or go hang out with your friends?
"Really, nothing. That's just life. Really this is our way of living, it is not our way of dying. It is our way of destroying shirts, but our bodies are just fine."
Lucy Devine