"In the heart of the Karakum desert of Turkmenistan the Darvaza Gas Crater or The Burning Gates give off a glow that can be seen from miles away during the dark night. The large crater is a result of a Soviet gas exploration accident in the 1950’s. It was created when a Soviet drilling rig was drilling for natural gas fell into an underground cavern resulting in a crater which today measures roughly 60 meters in diameter and 20 meters deep.
The huge crater was set alight shortly after being discovered and has been burning ever since. The recognizable smell of burning natural gas can be detected from a distance and becomes quite strong as you near the hot edge of the crater."
Text & see pictures: Johnhbradley.com
See it in Wikipedia: http://en.wikipedia.org/wiki/Darvaza