Mexico’s Cave of Crystals stunned geologists when it was first discovered in 2000. The underground chamber contains some of the largest natural crystals ever found – some of the selenite structures have grown to more than 10m long. Professor Iain Stewart got a rare glimpse of the subterranean spectacle while filming for the new BBC series How the Earth Made Us.

It’s here / C’est là : http://news.bbc.co.uk/2/hi/science/nature/8466493.stm

Cave of crystals of gypsum at Naïca, Mexico.