4. Cueva de los Cristales in Mexico
The Cueva de los Cristales, or Cave of Crystals, in Mexico is home to some of the world’s largest natural crystals, up to 36 feet long. For about 500,000 years, the cave produced these huge crystals in its stable natural environment with temperatures around a consistent 136 degrees and mineral-rich water that aided the crystal’s growth. The cave was discovered pretty recently in 2000 when mining exposed the crystal fortress by pumping the water out. Cueva de los Cristales is a tricky place to visit since you need to put on an insulated ice suit to endure the cave’s heat and can safely only spend about 10 minutes inside, but we’re up for the challenge to gaze upon the colossal crystals.