Naica Crystal Cave - Mexico

A team of international scientists explore a Mexican cave filled with giant crystals. With temperatures near 120 degrees Fahrenheit (48.8 Celsius), and over 80 per cent humidity, the cave is one of the
deadliest environments on earth. Without specialized suits and
equipment, the scientists would die in minutes. Their mission: to unlock
the secrets of the mysterious ancient crystals, some of the largest
ever discovered.