The Crystal Cave of the Giants, Mexico

Found deep inside a mine in southern Chihuahua, this giant cave contains some of the largest natural crystals ever found. They are a translucent gold and silver in color and come in many incredible forms and shapes. The cave is extremely hot with air temperatures reaching up to 58 °C (136 °F) with 90 to 99 percent humidity. The cave is relatively unexplored due to these factors. Without proper protection people can only endure approximately ten minutes of exposure at a time. Exploration hinted at the existence of further chambers, but further exploration would have required demolition of the crystals.