<p><a href="http://brusnichka.com/2008/03/26/darwaz-the-door-in-hell">Brusnichka.com</a> tells the story:</p>
Once the geologists were drilling for gas. Then suddenly during the drilling they have found an underground cavern, it was so big that all the drilling site with all the equipment and camps got deep deep under the ground. None dared to go down there because the cavern was filled with gas. So they ignited it so that no poisonous gas could come out of the hole, and since then, it’s burning, already for 35 years without any pause.
<p>Good photos on that page too.</p>