Fallingwater, Pennsylvania

Fallingwater remains the most celebrated private residence of the 20th century, consistently voted America's greatest building by architecture critics. Frank Lloyd Wright's 1939 masterpiece cantilevers its concrete terraces directly over Bear Run creek, with the living room floor incorporating the stream's unprocessed bedrock. The structure uses 30% less steel than typical cantilevered designs of its era, yet supports spans of over 50 feet. Its integration with nature outperforms #8 Hearst Castle's opulent but separated design, achieving a harmony that influenced modern architecture globally. The home's annual maintenance costs exceed $1.2 million, reflecting the preservation demands of its waterfall site.