Derweze, also known as the door to hell, is a 70 meter wide hole in the middle of the Karakum desert in Turkmenistan. The hole was formed in 1971 when a team of soviet geologists had their drilling rig collapse when they hit a cavern filled with natural gas. In an attempt to avoid poisonous discharge, they decided to burn it off, thinking that the gas would be depleted in only a few days. Derweze is still burning today 

(Source: goodnamesgone, via snorlax2-deactivated20120226)