We may think that most of the world's most amazing natural sights exist here on the surface of earth, however there are all sorts of natural wonders located beneath our feet.
Here are some of the world's most incredible underground locations, which are sure to delight everyone.
Cave of the Crystals, Chihuahua, Mexico
Located in a remote corner of northern Mexico, Cueva de los Cristales is a mesmerising place.
Discovered by miners drilling nearly 300m below the surface in 2000, the cave is home to hundreds of gigantic crystals, criss-crossing diagonally throughout the enormous, extremely humid, 58C space.
The largest crystal is some 12m in length, and the smallest look like flakes of frost ...