Crystal Cave of the Giants in Naica, Mexico

The Giant Crystal cave was discovered in April 2000 by miners who were excavating a new tunnel approximately 1000 feet below the Naica mine's surface. When they did this, it was almost as if a magical veil of reality was breached and an entirely new world was uncovered. Two caverns filled with the Earth's largest crystals were immediately revealed. The giant selenite crystals, were found to be as large as 50 ft long, 13 ft in diameter and 55 tons in weight, making them some of the largest natural crystals ever found. The crystals thrived in the cave's extremely rare and stable natural environment and were driven to such growth by the combination of intense temperature, humidity and mineral-rich water. With temperatures of 136°F and 90-99% humidity, the cave still remains relatively unexplored. When inside the great cathedral of crystals, the pressure of intense heat creates a gamut of emotions and perhaps hallucinations. Sadly some have suffocated, only to be found later, completely baked. The intense heat can prevent brain functioning and without the proper protection, one can only endure approximately 10 minutes of exposure at a time.

The Door to Hell in Derweze, Turkmenistan

The Derweze area is rich in natural gas. While drilling in 1971, geologists tapped into a cavern filled with natural gas. The ground beneath the drilling rig collapsed, leaving a large hole with a diameter of about 230 ft. To avoid poisonous gas discharge, it was decided to burn it off. Geologists had hoped the fire would use all the fuel in a matter of days, but the gas still burns 40 years later. Locals have dubbed the cavern "The Door to Hell".