Cave of the Crystals: Home to the World's Largest Crystals

Deep beneath Naica, Mexico, lies a cave filled with giant selenite crystals, some over 11 meters long and weighing 12 tons. Discovered in 2000, the cave is a natural wonder, but its extreme heat and humidity make exploration nearly impossible without special gear. Scientists have studied these crystals to understand their slow growth over half a million years, and have even found ancient bacteria trapped inside.