In 1971, Soviet geologists drilled into a cavern of natural gas near the Turkmen village of Derweze.
The ground beneath collapsed and in order to control the emission of poisonous methane gas they decided to set the crater on fire expecting the fire to burn out in a few days. That was 40 years ago and it’s still burning today. Hence the name “The Door to Hell”.
Others gates to hell also exist around the world.