Finally, a pair of daredevils has descended into one of the world's largest caves.
They dropped down just to see if they could get back out.
Here's their story from Errol Barnett.
This is Majlis al Jinn, the cave of spirits, located in the mountains of Oman.
It's said to be the second-largest cavern in the world.
Outside though, it just looks like a hole in the ground.
But once you see inside, it becomes beautiful and immense --
big enough to hold the Great Pyramid of Giza.
Few have been here and it's believed no one's ever tried to climb out, until now.
Two expert climbers, Stefan Glowacz of Germany and Chris Sharma of the U.S.,
recently teamed up for this first-of-its-kind challenge.
It's really overwhelming, so I wasn't sure that we were gonna be able to do it.
First they rappel more than 500 feet, or about 160 meters, straight down to the cave floor.
Then, they begin their ascent, slowly, taking days to climb back to the top.
To get there, they have to make one of the most difficult climbs in the world.
You can say that maybe it's the biggest roof on earth, and maybe it's a world record,
but this was not the objective for us, to climb the biggest and maybe a world record there.
But, we wanted to climb this unique project.
Now there were some close calls. Watch this as a safety rope saves Sharma from a serious fall.
But they keep going, scaling the vertical wall and then the cave ceiling where they have to climb upside down.
During an especially difficult pitch, Glowacz falls,
hurting his hand and leaving Sharma to finish the difficult stretch.
Finally, after 12 grueling days, the two climbers complete their amazing ascent.
You know, to get the chance to come to such a far-away country and to such a remote, crazy location like that cave,
and to get to climb with Stefan has been really, really unforgettable.
Afterward, congratulations from locals who gathered to watch.
The climbers say their blisters will soon heal, but the memory of their accomplishment will last a lifetime.