Danakil Depression, Ethiopia  Photograph by Carsten
Peter/National Geographic  Disks of travertine, a calcium-rich
deposit, ring a hot spring in Ethiopia's Danakil Depression.
Afar tribeswomen extract water from this forbidding landscape by
building small stone towers over the geothermal vents. The steam
condenses, and the water runs into a reservoir. When it cools,
the women pour it into their goatskin bags.