A relic of Soviet-era experiments, this hellish crater has been on fire since 1971

Back in the 1970s, a group of Soviet geologists drilling for oil in Turkmenistan hit a natural gas pocket and accidentally created a huge sinkhole. It's not exactly clear how it happened, but soon after the sinkhole was set on fire and his been burning ever since. The "Gates of Hell" crater is Turkmenistan's most visited tourist site, but its environmental impact may finally lead it to be extinguished by authorities.