It looks like a crater with a volcanic lava lake, but it is not. It is said that the hell is located underground. In this case, "The Door to Hell" is this site in Uzbekistan, located close to the small town of Darvaz.

This phenomenon started during the Soviet times, 35 years ago. Geologists and miners were drilling inside a mine. At a point, the gas buildup impeded any further activity. Employing the normal mindset of the times, the team planned to fire the gas and return when it was totally burned. A huge gas explosion formed the 30 m (100 ft) wide crater. The huge hole engulfed the entire drilling site with the equipment and camps.

The fact is that the site has been incessantly burning ever since, and the deposit seems to contain yet a lot of gas to burn. The inhabitants of the area had to be removed meanwhile.

A similar situation started 46 years ago in US. The fire set to burn a landfill close to Centralia, a small town in Pennsylvania, somehow reached a coal mine. For some time, the mine burned without anyone to notice, but in time the inhabitants got sick from carbon monoxide and sink holes opened up. The ground reached temperatures of 172°F (77.8°C).

What is more interesting is that even the volcanic phenomena of continuously boiling lava lakes are extremely rare: just three cases are known on Earth.

Most volcanoes manifest through occasional eruptions, then their lava hardens, like the crust on a wound, but this is not the case of Erta Ales in Ethiopia, Puuoo in Hawaii and Erebus in Antarctica. The area of Erta Ales is a feared and taboo place, being named... "The dwelling of the Devil" by the local Afar nomads, who are Muslims. In time, this volcano swells its lava lake before retracting it back. Still, from time to time, the lava overflows the edges of the crater, as it did in 1974.