Giant Crystal Cave Comes to Light

Check out the photos in this National Geographic article, Giant Crystal Cave Comes to Light.
I include one photo and one sentence to pique your interest.
--pws

• A sort of south-of-the-border Fortress of Solitude, 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 36 feet (11 meters).