Permafrost
Planet Earth's surface has regions cold enough for the ground to remain frozen year round, called permafrost. Permafrost is found in Earth's Polar regions, and on high mountain tops.
Permafrost requires special construction techniques, when building structures, roads, railways and pipelines, due to frost heave.
Scientists estimate that the World's permafrost has sequestered large amounts of Carbon, and Methane, which will accelerate the rate of global warming, as the World's permafrost melts.
Most permafrost deposits have been frozen since at least the last ice age, and relatively intact carcasses of extinct mammals, like Mammoths, have been found, when they thaw.