A crater in Turkmenistan at the Karakum Desert has been burning for 40 years now. In 1971 Soviet Geologists were drilling in the desert when they drilled into a natural gas pocket.
The earth collapsed creating the crater. Scientists who feared the crater would release poisonous gases into the air lit the crater on fire to limit the amount of gas leaking into the air. The fire has now burned ever since. There is no telling how much gas is in that crater.
The locals have named the crater the “The door to hell”.
Another hole left behind by Soviet Drilling: