Fallingwater may look like a loose pile of concrete slabs about to topple into the stream... but there is no danger of that! The slabs are actually anchored through the stonework of the hillside. Also, the largest and heaviest portion of the house is at the rear, not over the water. And, finally, each floor has its own support system.

When you enter the recessed front door of Fallingwater, your eye is first drawn to a far corner, where a balcony overlooks the waterfall. To the right of the entryway, there is a dining alcove, a large fireplace, and stairs leading to the upper story. To the left, groups of seating offer scenic views.

Fallingwater, also known as the Edgar J. Kaufmann Sr. Residence, is a house designed by American architect Frank Lloyd Wright in 1934 in rural southwestern Pennsylvania, 50 miles southeast of Pittsburgh. The house was built partly over a waterfall in Bear Run at Rural Route 1 in the Mill Run section of Stewart Township, Fayette County, Pennsylvania, in the Laurel Highlands of the Allegheny Mountains.

http://architecture.about.com/od/franklloydwright/ig/Frank-Lloyd-Wright/Fallingwater.htm

Hailed by Time magazine shortly after its completion as Wright's "most beautiful job it is also listed among Smithsonian magazine's Life List of 28 places "to visit before ...it's too late Fallingwater was featured in Bob Vila's A&E Network production, Guide to Historic Homes of America It was designated a National Historic Landmark in 1966 In 1991, members of the American Institute of Architects named the house the "best all-time work of American architecture" and in 2007, it was ranked twenty-ninth on the list of America's Favorite Architecture according to the AIA