Beneath the sands of Mexico are crystals the size of Buicks.

They call it the Crystal Cave of Giants. Up to fifty feet tall, four feet wide, and all a thousand feet underground, these crystals were discovered when a couple of workers drilled a new tunnel into the Naica mine, which was already famous for the crystal-filled ‘Cave of Swords’ a few hundred meters away. Suddenly, the Cave of Swords came up second-best.

The entire cave stays around 136° F, thanks to nearby magma vents - a fever above 108° can cause brain damage. This heat caused the crystals to form: water that once filled this cave was rich in anhydrite, a mineral that dissolves into gypsum at high temperatures. From there, the gypsum can crystallize into the immense but delicate structures like the ones found here. They’re still soft enough to scratch with a fingernail.

Geologists would like to open the caves up to the public, as soon as they add some air conditioning. Luckily, they don’t need to worry about looters: in the first few days after its discovery, one particularly stubborn fellow sneaked in with a few plastic bags filled with fresh air. He lost consciousness, and was later found ‘thoroughly baked.’