Cantilevers hold up a surface or room without themselves being supported at their outer end. Many outdoor balconies are cantilevered, and theater balconies may be as well. A cantilevered bridge may have a huge span (as long as 1,800 feet) built out on either side of a single large foundation pier. Architects sometimes use cantilevered construction to produce dramatic effects; Frank Lloyd Wright's "Fallingwater" house, which extends out over a rocky river, is a famous example. But the Grand Canyon's "Skywalk" has become perhaps the best-known piece of cantilevered construction in America.