World's Coolest Caves
Carsten Peter/Speleoresearch & Films/National Geographic Stock
Cave of the Crystals (Cueva de los Cristales): Mexico
Translucent grayish-white selenite crystal columns, some up to 36 feet long, shimmer in a chamber called Crystal Cave of Giants, 1,000 feet underground in the Naica Mine near Chihuahua. Crystal obelisks several feet wide sparkle in a professional caver’s lights, but temperatures up to 136 degrees with more than 90 percent humidity make visiting extremely dangerous even for the few researchers allowed in.
Why It’s Cool: Nothing remotely like these gigantic crystals exists anywhere else, not even in nearby caves. And the Cave of Crystals was discovered only by chance in 2000 when miners pumped water out of the first 30-by-90-foot chamber.