Denver artist Patrick Marold makes pieces that address environmental issues, and his latest, "The Windmill Project," in Vail, is staggeringly large, with 2,700 separate elements. Each of those comprises a ten-foot tall transparent tube, which houses a light and is topped by three rotating prongs that terminate in hollow half-spheres. As the "windmills" catch the breeze with their cups, they power the lights. This ambitious sculpture, installed on the hillside above the seventeenth green at the Vail Golf Course, is temporary and will be gone with the wind come Earth Day, April 22.