NGC goes inside one of the greatest natural marvels on the planet - a
giant crystal cave described as Superman's fortress, with magnificent
crystals up to 36 feet long and weighing 55 tons. A team of experts
venture into the cavern, enduring scorching-hot temperatures that could
kill a human after just 15 minutes of exposure. They'll push the
boundaries of physical limitation to explore a crevasse that could lead
to another - and perhaps more spectacular - crystal cave.