It’s a staggering 300 metres underground, features amazing 11-metre-tall crystals – and has a deadly 90% humidity level

The aptly named Cave of Crystals, in Chihuahua, Mexico, is buried around 300 metres underground and contains giant gypsum crystals up to 11 metres long.

Some are big enough to walk on and are so impressive they earned the cave its alternative moniker, the ‘Sistine Chapel of crystals.’

The cave sits on a fault line above a chamber of magma. Millions of years ago, scorching magma forced mineral-rich ground water up through the rock. This created caverns in the limestone and formed deposits which then slowly began to cool and crystallise. Eventually, the temperature stabilised at around 58 degrees Celsius, creating the perfect conditions for the crystals to grow…but deadly conditions for people. 

Whilst 58 degrees isn’t necessarily a dealbreaker, the high level of humidity is. It stands at 90%, which means the human body is unable to cool itself down by sweating. Without specialist equipment, any person in the cave would quickly overheat, so this is one place best viewed in a photograph.