Hidden away deep inside Earth’s crust is a magical subterranean world of caverns, such as these stunning examples
Psychedelic salt mine
A former salt mine in Yekaterinburg, Russia, is now one of the world’s most colourful caves. More than 200 m (650 ft) underground, its patterned rainbow walls are caused by the mineral carnallite swirling in layers through the rock.
Crystal caves
Only discovered in 2000, the Cave of the Crystals in Mexico is part of the Naica Mine and is home to the largest crystals in the world. Some of the giant selenite crystals it contains have grown to more than 10 m (33 ft) in length.
Marble marvels
Crashing waves have eroded and sculpted Patagonia’s Marble Caves. One of the caves is called the Marble Cathedral, after its distinctive sweeping arches. Eye-catching reflections of the shimmering blue water dance across white marble ceilings.
