Grown naturally, Superman's Fortress of Solitude would have taken…

The Crystal Cave — known to many as La Cueva de Los Cristales — is buried 300 meters below the Earth's surface, sequestered away in the Naica ore mines of Chihuahua, Mexico. Bursting from the top, bottom, and sides of the cavern's walls are otherworldy outcroppings of gypsum crystal. Many are too big to wrap your arms… » 1/18/12 1:00pm 1/18/12 1:00pm