There are no written Soviet records, no logs, no official drilling reports, and no confirmation that they'd lit it intentionally – but there's no disputing a ~100-foot (~30-m) deep, 226-foot (69-m) wide pit of relentless fiery fury that's been burning for around 50 years in the Karakum Desert of Turkmenistan.
Archived version: https://archive.is/newest/https://newatlas.com/environment/darvaza-gas-crater-door-to-hell-closing/
Disclaimer: The article linked is from a single source with a single perspective. Make sure to cross-check information against multiple sources to get a comprehensive view on the situation.