This famous house sits atop a waterfall [video]

American architect Frank Lloyd Wright designed more than 1,000 structures during his lifetime. One of the most famous is Fallingwater, a house in rural, southwestern Pennsylvania.

The house is called Fallingwater and for a reason: It sits on top of a waterfall, created by a mountain river named Bear Run. The waterfall becomes part of the house. You hear it in one of the bedrooms. You see it under your feet in the living room.

The home, now a museum, combines human-designed forms with nature, incorporating the stone, flowers and water that are in the landscape. It has many open spaces. Instead of art or photographs on the walls, there are large windows.

Wright designed the house in 1935 for Edgar and Lillian Kaufmann, who owned a department store in Pittsburgh. The structure was so interesting that it and Wright were on the cover of Time magazine in 1938.

Smithsonian Magazine calls Fallingwater one of the few places that Americans must see.

Over the past 50 years, more than 4 million people have done so. Many famous people visited Fallingwater, including scientist Albert Einstein, then-President Franklin Delano Roosevelt and actress Ingrid Bergman.

April 22 is Earth Day — celebrate by taking your own tour. Just  click on the video below.