Door to Hell
Door to hell is situated in Dervaze Turkmenistan and is a hole of natural gas which collapsed into the earth in 1971 . Geologists have put fire to this hole to stop the methane gas from spreading and it has been burning since then. The width of this hole is 69 metre and depth 30 meter.
Image Source :http://www.huffingtonpost.com/entry/door-of-hell_n_4311694.html?section=india