CIGLENA, Croatia - Hidden in the rolling hills of the Croatian countryside, a futuristic structure that looks a little like a flying saucer is what backers say is the hope for the region's emissions-free future.
In a part of Europe that still generates much of its electricity by burning natural gas and coal, some green advocates say they should look deep beneath their feet to harness the power of the earth's core. Croatia and its neighbors sit on top of a patch of unusual geology where the vast heat at the center of the world has an especially easy time coming close to the surface.