41 years and still burning.

While drilling in 1971, Soviet geologists tapped into a cavern filled with natural gas.The 

ground beneath the drilling rig collapsed, leaving a large hole with a diameter of 70 metres 

(230 ft). To avoid poisonous gas discharge, it was decided the best solution was burn it 

off.Geologists had hoped the fire would use all the fuel in a matter of days, but the gas is 

still burning today. Locals have dubbed the cavern "The Door to Hell".