In the year 2000, miners drilling deep under a mountain in Naica, Mexico, broke through into a chamber that looked like the lair of a giant. Beams of clear gypsum crystal as long as buses crisscrossed the cave, some weighing 55 tons. They are the biggest natural crystals anyone has ever discovered.
The crystals grew slowly over hundreds of thousands of years. The cave was filled with warm, mineral-rich water heated by magma far below. Over time, tiny crystals in the water added themselves layer by layer, like sugar building up on a string, until they reached the size of telephone poles.
The cave is now one of the most dangerous places a human can visit. Inside it stays around 113°F (45°C) with almost 100% humidity, hot enough to cook a person from the inside out. Scientists wear ice-cooled suits and respirators and still have to leave after about ten minutes.
