Cueva de los Cristales

Buried 300 meters below Naica mountain in the Chihuahuan Desert, this astonishing cave was discovered by two miners in 2000. Mexico's Cueva de los Cristales (Cave of Crystals) contains some of the world's largest known natural crystals - translucent beams of gypsum as long as 11 meters. The cave reminds of Superman’s Fortress of Solitude. New studies report that for thousands of years the crystals thrived in the cave's extremely rare and stable natural environment. Temperatures hovered consistently around a steamy 55 degrees Celsius, and the cave was filled with mineral-rich water that drove the crystals' growth. The Cave of Crystals is a horseshoe-shaped cavity in limestone rock about 10 meters wide and 30 meters long. The volcanic activity that began about 26 million years ago created Naica mountain and filled it with high-temperature anhydrite. When magma underneath the mountain cooled and the temperature dropped, the anhydrite began to dissolve. The anhydrite slowly enriched the waters with sulfate and calcium molecules, which for millions of years have been deposited in the caves in the form of huge selenite gypsum crystals. The humidity is 100% inside the cave which in combination with the extreme heat, you cannot visit this wonder without a heat resistant suit. That is also cool.