Derweze Crater, Turkmenistan
In the hot Karakum desert in Turkmenistan, near the 350 person village of Derweze, is a hole 328 feet wide that has been on fire, continuously, for 38 years. While drilling in 1971, Soviet geologists accidentally found an underground cavern filled with natural gas. The ground beneath the drilling rig collapsed, leaving a large hole with a diameter of about 50-100 meters. In order to avoid poisonous gas discharge, it was decided to burn the gas. Geologists had hoped the fire would go out in a few days but it has been burning ever since.