Visit Atlas Obscura for some of “the world’s wonders, curiosities and esoterica” including an article on The Gates of Hell, a fiery 328 ft wide hole near small village of Derweze, Turkenistan, which has been burning ever since a Russian drilling rig punctured a gas-filled cavern. They lost their rig, as it fell into the hole, and gas started leaking out. Geologists decided to burn off the gas, but the fire has never gone out – even though the original incident was 39 years ago.
There’s also an underground fire burning in Centralia, Pennsylvania, which started in 1962. The town has been condemned and residents moved out. It’s not known when, if ever, they might be able to return.
Hat tip: @zambonini