SPRING GREEN, Wis. (AP) _ Thousands come each year to the Wisconsin River valley where Frank Lloyd Wright built his home and tested his ideas about building in harmony with nature.

Nestled on a hillside overlooking the river, Wright's Taliesin has the cantilever roofs, wide windows, great room and open floor plan that became some of the architect's trademarks.

The design concepts, revolutionary in Wright's time, are now widely taught in architecture schools and common among builders concerned about the environment.

"He spans generations," said Robert Mattison, a professor of art history and architecture at Lafayette College in Easton, Pa. "There is a parallel between (Wright's) idea of organic architecture and what we call sustainability today, and that's what makes it interesting."

Wright is often associated with Chicago, where he established his career, and Arizona, where he spent much of his later years and established his foundation.

But the self-proclaimed "world's greatest architect" had lifelong ties to the southwestern Wisconsin valley settled by his mother's family. He was born in 1867 in nearby Richland Center and spent many summers working on his uncles' farms in Spring Green.

The village sits amid the rolling hills of Wisconsin's Driftless Area, so-called because the glaciers that scraped the rest of the state bypassed it. Here, Wright developed an appreciation for nature and many of the ideas he would later incorporate in his work.

Wright returned to Spring Green in 1911 and built Taliesin on a hill overlooking the Wisconsin River. He used local limestone and mixed sand from the river into his plaster.

Wright's use of indigenous materials reflects a desire to connect with the land, Mattison said. "But that can also make sense in terms of sustainability because you're shipping the materials less distance."

Wright used glass to great effect in Taliesin's living room, where tall windows provide a spectacular view and further the architect's goal of breaking down barriers between the interior and exterior.

The windows also provide natural light, which is defused by the overhanging roof so that the house remains cool, Mattison said: "That's something we think about as sustainable today."

Wright rebuilt the house twice, after fires in 1914 and 1925. He expanded the home each time so that the complex with his studio and stable now has about 24,000 square feet.

The agricultural wing was converted to living quarters in 1932 for members of the Taliesin Fellowship, now the Frank Lloyd Wright School of Architecture. Some of the original fellowship members still live there, while current apprentices stay at the nearby Hillside Studio, where they can be seen working during some tours.

Wright treated his home as a laboratory, making changes for the rest of his life. He didn't worry too much about the quality of construction because at any moment he might have a new idea and renovate again.

Thus, in the living room and alcoves, gaps between the window panes and stone walls let in air and moisture. Wright didn't bother to have grooves cut into the stone so the glass could be inserted and sealed.