Crystal Underworld

It looks like Superman’s Fortress of Solitude and is nearly as hard to get into, but that hasn’t stopped explorers from uncovering new secrets in and around Mexico’s deep, deadly hot Cave of Crystals.

Mineral Garden

Pictured in December 2009, crystalline “cauliflower” sprouts from the floor and ceiling of the newfound Ice Palace, found about 500 feet (150 meters) underground, above the Cave of Crystals

The Ice Cube

In 2009 an explorer in the Cave of Crystals chills in the Ice Cube (right), an air-cooled, plastic-sided tent intended to allow for two-hour missions in the Naica caves’ deadly heat and humidity.In this cave’s extreme heat and moisture, though, the portable shelter never cooled down enough to bring the explorers’ overheated bodies back to safe levels.

The Sword in the Stone

So-called Excalibur rises from the floor of the Cave of Crystals. The bladelike beam displays the jewel-like contours so far seen in no giant crystals outside the Cave of Crystals, according to mineralogist John Rakovan of Miami University in Ohio

Spun Crystal

Like fiber optic threads, rare crystal formations sparkle on the floor of the newfound Ice Palace cave in 2009

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