These remarkable caving pictures show thrill-seeker Dave Bunnell descending into Mexico’s El Sotano de las Golondrinas – aka the Basement of Swallows.
It is so deep that clouds form inside of it and measuring in at a staggering 1,200ft, it is one of the most dramatic free fall pits in the world.
The 61-year-old told Caters News Agency: "It's such a different world it sometimes seems like being on another planet.
“So the otherworldliness of it, and that you never know what may lay around the next corner, when exploring a new cave, even a small one can give you these feelings like no other."
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The pit was first descended in December of 1967 by a trio of Americans and since then cavers from all over the world have visited it.
It’s total depth is 1,638ft with the final few hundred feet accessible via a pit series called The Crevice.