Although Wright designed and built over 400 buildings, 300 of which survived as of 2005.  Several are architectural jewels.  During the 1920s, Wright designed Graycliff, one of the most innovative residences of the period.  The Graycliff estate was built on a bluff overlooking Lake Erie and was one of the first buildings to use large amounts of stone, which Wright believed to be an essential part of every building.  One of Wright's most famous private residences, Fallingwater, was built from 1935 to 1939, at Bear Run, Pennsylvania near the family’s favorite waterfall.  Wright suspended the house over the waterfall, making it appear part of the home, the ultimate example of connecting a structure with its natural setting.  The Solomon R. Guggenheim Museum in New York City occupied Wright for 16 years, from 1943 until 1959 and is probably his most recognized masterpiece.  With its spiraling ramp and swelling profile the building has become a cultural icon throughout popular culture.