At the southernmost tip of South America, the towering Andes rise sharply from the deep waters of the Pacific, creating a rugged expanse of coastal islands, dense rainforests and snow-capped glaciers. But the transnational hydroelectric company HidroAysén wants to build five mega-dams on two of Patagonia's pristine rivers that could lay waste to one of the world's last unspoiled regions and flood thousands of acres of wildlife habitat.