In 1950, at 83, Frank Lloyd Wright designed a house for a private island on Lake Mahopac, about 50 miles north of New York City. He dreamed it might surpass Fallingwater, his 1935 masterpiece—but then the client ran short of funds, and the house was shelved for almost 50 years. Now, after eight years of planning and construction, the house is finally complete—5,000 spectacular square feet of mahogany, lake stone, hand-troweled cement, and triangular skylights.

But no house, least of all a posthumous construction from the twentieth century’s most famous architect, is an island, and this one has become a particularly hot piece of intellectual real estate. There are those who celebrate its realization: It’s used in the packaging of the Apple-based architecture software that helped bring the design to life and is the subject of an upcoming PBS documentary. And there are its haters: architects, scholars, and amateurs who say it’s not Wright’s real vision—the stones jut too much, the skylights should be flat, not domed, and so on. As it stands, the house is officially unofficial. The Frank Lloyd Wright Foundation’s chief executive officer, Philip Allsopp, states bluntly, “It’s not a Frank Lloyd Wright house, because it hasn’t been certified by the foundation.”