By Lucie Young
Photographs by Richard Barnes

James Turrell is known for making art out of light and thin air, challenging our notion of how we see. The artist says that his work is ''like trying to make the emperor's clothes visible.'' Turrell calls his latest work -- a 350-square-foot concrete ''skyspace'' -- a garden folly. It hangs 200 feet above Benedict Canyon in Los Angeles, cost more than a million dollars and took 13 years to complete because of its precarious site. It even outlived the renowned modernist architect John Lautner, whose office got the commission, and was completed by Lautner's project architect, Duncan Nicholson.

From the outside, this folly looks like a cross between a bunker and a concrete brioche. Inside, it is like an isolation tank or a private chapel, filled with expensive nothingness: curved walls, a floating floor, a rectangular opening for a window and another, much larger one in the roof. Turrell likens the spare interior to Plato's cave, in which ''we realize that we perceive the outside reality incompletely. We think we are seeing the whole, but in fact we are only seeing part. We think we exist independently of nature, but we are very interrelated. We even influence the colors that we see.''

So does Turrell. Like the Wizard of Oz, he pulls the strings to transform what we see. More than 5,000 computer-programmed L.E.D. and incandescent lights, concealed beneath the floor, wash the walls with a symphony of colors -- which in turn transform the sky outside from blue to red to molasses black. At times it feels as if the whole room is pulsating with energy. ''The colors work on the senses like abstract music,'' Turrell said. ''It is profoundly emotional work.''

Often the reaction it elicits is awe. ''Everyone's mouth falls open when they see it,'' said James Goldstein, an entrepreneur, who commissioned the skyspace. Twice a day he navigates the 230 or so steps down a near-vertical hillside from his house to visit his folly, which is equipped with a wet bar and a sound system -- two distinctly un-Turrellian additions. The artist would prefer that his patron listen to the sounds of the planets, but he doesn't dictate how the space is to be used. Turrell's own dream (apart from completing the Roden Crater, the celestial observatory that he has been building in a sleeping Arizona volcano for the last 30-plus years) is to build a sky-viewing house where he can live, eat, bathe and sleep year-round. ''Light is strangely fragile,'' he said. ''It needs to have a home where it is cared for.''