And that door to hell is, in fact, a big sinkhole where natural gas burns like crazy. That sinkhole is 20 meters deep and 70 meters in diameter and it is located in Karakum Desert, Turkmenistan, near the village called Darvaza (or Derweze).
That place is also called the Darvaza Gas Crater and it is a tourist attraction. It will burn fire for many years to come so all you need to is to prepare enough money and then go there.
How did that happen? Some Soviet geologists tapped into a gas cavers in 1971 and the ground beneath the drilling rig collapsed. The exact location: 40°15′10″N 58°26′22″E.