The Bureau of Reclamation accepted Breuer’s proposal for the design of the Grand Coulee Third Power Plant and Forebay Dam in February of 1968. Breuer’s project is part of a larger hydroelectric complex that bridges the Columbia River in Washington State. Working with his partner Hamilton Smith, Breuer created a sloping dam of sheer concrete 550 feet high and wide enough at the top to carry a two-lane highway. A glass elevator connects the top of the dam to the top of the power plant below, where visitors can access an observation deck cantilevered out over the river. The source of the power plant’s faceted concrete exterior can be traced back to the folded concrete walls of the assembly hall for the UNESCO headquarters complex. The massive internal space of the power plant houses giant power generators installed in covered, circular wells that punctuate the black terrazzo floor. The Bureau of Reclamation was so pleased with Breuer’s design that they asked him to update the older segments of the dam. That commission was never realized, but Breuer did design a Visitor’s Center for the dam that was completed in 1978.