The “Door to Hell” is a natural gas field that has been burning continuously since it was discovered in 1971.
The gas reserve found here is one of the largest in the world. The name "Door to Hell" was given to the field by the locals, referring to the fire, boiling mud, and orange flames in the large crater, which has a diameter of 70 metres. The hot spots range over an area with a width of 60 metres and to a depth of about 20 metres.
The site was identified by Soviet engineers in 1971. It was originally thought to be a substantial oil field site. The engineers set up a drilling rig and camp nearby, and started drilling operations to assess the quantity of oil available at the site. When they instead found gas, the ground beneath the drilling rig and camp collapsed into a wide crater and disappeared.
Expecting dangerous releases of poisonous gases from the cavern into the nearby towns, the engineers saw it as best to burn the gas off. The gas was estimated to burn out within a few weeks, but it has instead continued to burn for more than four decades after it was set on fire.
The crater was featured in a Die Trying episode titled "Crater of Fire". Explorer George Kourounis became the first person to ever set foot at the bottom, gathering samples of extremophile microorganisms. The episode was broadcast on the National Geographic Channel on July 16, 2014.
Image source: "Darvasa gas crater panorama" by Tormod Sandtorv - Flickr: Darvasa gas crater panorama. Licensed under CC BY-SA 2.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Darvasa_gas_crater_panorama.jpg#/media/File:Darvasa_gas_crater_panorama.jpg