Wright responded to the family's love for a waterfall on Bear Run, a rushing mountain stream in Western Pennsylvania. Mimicking a natural pattern established by its rock ledges, Wright placed the house over the falls in a series of cantilevered concrete "trays," anchored to masonry walls made of the same Pottsville sandstone as the rock ledges. Although the house rises over 30' above the falls, strong horizontal lines and low ceilings help maintain a sheltering effect. Almost as much floor space is taken up by outdoor terraces as indoor rooms.

I think this is a design masterpiece, but we have to be clear - it is no engineering masterpiece.

An engineer must achieve excellence in three dimensions: design, economics, and operational survivability or quality.

Frank Lloyd Wright had only to achieve excellence in the first of these. He was building for people for whom cost was no object, and he exceeded materials design parameters so that within the first 25 years, the building was collapsing and had to be restored at a cost of 11 million dollars.