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While drilling in 1971 geologists accidentally found an underground cavern filled with natural gas. The ground beneath the drilling rig collapsed, leaving a large hole with a diameter of about 50-100 meters. To avoid poisonous gas discharge, it was decided to burn the gas. Geologists had hoped the fire would go out in a few days but it has been burning ever since. Locals have named the cavern The Door to Hell. As Darvaza no longer has an airstrip, the crater’s site is too far from the capital to send a foam plane to put the blaze out.