8. The Door to Hell, Karakum Desert, Turkmenistan
Darvaza Crater, or the "Door to Hell," is home to a fire that has been raging for no less than 42 years. The dangerous fire pit was caused by Soviet geologists drilling in the area in the early '70s.

After their drilling rig collapsed, a gigantic crater formed, and geologists decided to let the gas burn off naturally to avoid a poisonous discharge. They assumed it would burn off in a matter of days, so no one could have predicted that the fire would still be burning today...