IVANPAH, CALIFORNIA, SEPTEMBER 18 2012: An aerial view of Tower One's heliostats at the Ivanpah Solar Power Facility. Located in the Mojave Desert 40 miles southwest of Las Vegas, The Ivanpah Solar Power Facility is a solar thermal power project, currently under construction, with a planned capacity of 392 megawatts, enough to power approximately 140,000 houses. It will deploy 170,000 heliostat mirrors spread over 4,000 hectares, focusing solar energy on boilers located atop three solar power towers, generating steam to drive specially adapted steam turbines The project, developed by BrightSource Energy and Bechtel, will cost $2.2 billion and be the largest solar farm in the world (photo Gilles Mingasson for the Smithsonian).