McMurdo Dry Valleys, Antarctica
The largest ice-free region in Antarctica is a windswept, frozen desert whose rugged terrain looks as if it belongs on Pluto rather than our planet. Covering 9,300 square miles (15,000 square kilometers), its valleys were carved by glaciers that long ago retreated, leaving in their wake a broken layer of boulders, gravel and pebbles, all of which have been worn down by the harsh weather and sorted by the strong winds.
The surface contains deposits of marine sediments, in addition to sand dunes and ash, and covers a layer of soil that's millions of years old. Scientists like the Dry Valleys because the lack of ice makes it easier for them to get a look at the current geological processes affecting Antarctica [source: McMurdo].