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.
ADDENDUM: Post title I should have thought of from @Durf: “It’s the Glittering Caves of Aglarond!”