A photo of the "Burning Gas Crater" in Darvaza, Turkmenistan. This so-called "door to hell" was created as a result of a mining accident in 1971 when the drilling rig collapsed, generating poisonous gas that necessitated burning off whatever natural gas there was at the drilling site. But the gas source, presumed to be exhausted in a few days, ended up burning for 40 years and counting.