Many fabulous and important objects have been found inside of caves, but few of them can rival the truly gargantuan crystals resting beneath a mine in Naica, Mexico.

Many fabulous and important objects have been found inside of caves, but few of them can rival the truly gargantuan crystals resting beneath a mine in Naica, Mexico, reports National Geographic. 
According to the BBC, those who travel deep into the Earth to catch a glimpse of the Cave of Crystals are typically left awestruck by the dazzling sight.
Journalist Neil Shea wrote of the experience, “I crawled among the world's largest crystals, a forest of them, broad and thick, some more than 30 feet long and half a million years old. So clear, so luminous, they seemed extraterrestrial.” 
Although the sight may be breathtaking, taking it in is not without discomfort. 
Temperatures inside the cave can climb over 110 degrees Fahrenheit, and humidity is estimated to be right around 100%.