Fallingwater, designed by Frank Lloyd Wright, was built in 1936 for a Pittsburgh department store owner. The house and grounds were later presented to the Western Pennsylvania Conservancy. The key to the setting is the waterfall over which the house is built. Wright envisioned the house as a series of horizontal concrete "trays," extending as terraces from the living levels. The horizontal reinforced concrete members were spaced one above the other, separated by vertical masses of local sandstone.

The concrete trays are structural on their lower surfaces. Above the structural surface in many areas is an air space, divided by small concrete ribs that support wood floors covered with waxed flagstone from nearby quarries. The feeling is of wet rock in keeping with the ambiance of rushing water and projecting boulders. The captive airspace allows the stone floor to be well insulated and comfortable even to bare feet.

Wright had a deep appreciation of the plasticity and structural integrity of concrete, which was the ideal medium to execute his design. He said that reinforced concrete was absolutely necessary to building a residence. Concrete could be cast into any form; it was completely plastic; and it had the exceptional property of growing ever stronger with age. When reinforced with steel its tensile strength was suitably enhanced. Concrete made Wright's cantilever's possible, as he used parapets and reinforced concrete beams to stiffen and support them. In the words of Fallingwater's original owner, the house is a lasting testimonial to architectural genius. This perfect blending of nature with the universal building materials, stone and concrete, is a great performance indeed.