Darvaza Gas Crater
You'd be hard-pressed to find a hole in the ground stranger than the Darvaza Gas Crater. Located in the Karakum Desert of Turkmenistan, this strange formation is not the impact crater of an asteroid but the result of a drilling operation gone bizarrely wrong. In 1971, the Soviet Union sent geologists into the region to search for deposits of natural gas. While drilling just outside of the village of Darvaza, they broke into a huge underground cavern filled with the gaseous fuel that promptly swallowed their equipment. They then decided that the safest thing to do was to burn off the gas, so they set the crater on fire. Forty years later, it's still burning.
The Darvaza Gas Crater measures about 300 feet (91 m) across, and is an extraordinary sight for any traveler willing to venture out to the remote landmark [source: Travel and Leisure]. Its glow can be seen from the nearest road, which is a two-hour walk across the desert. A peek into the hellish crater reveals sand and rock debris licked by patchy flames of burning natural gas. Given the pit's resemblance to Biblical visions of the underworld, locals have appropriately nicknamed it the "Door to Hell." Interestingly, this fiery crater is not the only drilling-induced anomaly in the Karakum Desert; two other collapsed caverns in the area contain bubbling mud and water.