The McMurdo Dry Valleys | A row of valleys in Antarctica. It has many interesting geological features including Lake Vida & the Onyx River. The valley's floor occasionally contains a perennially frozen lake with ice several meters thick. It is also one of the world's most extreme deserts under the ice, in the extremely salty water, live mysterious organisms. Scientists consider the Dry Valleys perhaps an important source of insights into possible extraterrestrial life.
While drilling in 1971 in Derweze (in the middle of the Karakum Desert), Soviet geologists tapped into a cavern filled with natural gas. The ground collapsed, leaving a 230-ft hole. To avoid poisonous gas discharge, they decided to let it burn off (thinking it would be a matter of days). It's still burning today, earning the nickname "The Door to Hell".