-By Michael Webb

"Light is strangely fragile—it needs to have a home where it is cared for," says James Turrell, who has been creating such havens—in hotel rooms, residential backyards, and museums—for the past 40 years. He was born to a Quaker family in Pasadena, Calif., in 1943, and he remembers: "My room had windows on three sides, and my first experience with light came from drawing constellations on the glass so that I could see stars by day and learning that light conceals as well as it reveals." He studied the psychology of perception at Pomona College and followed his father's example in learning to fly, which brought him even closer to the source of natural light.

Soon after he began to create light works, Turrell began an aerial search for the world's largest canvas: a remote, symmetrical volcano he could turn into an instrument that would bring the cosmos into focus. In 1974, he bought Roden Crater, a volcano that has been dormant for the past 300,000 years, and a huge swathe of grazing land around it, 40 miles north of Flagstaff, Ariz. He moved to a ranch house to supervise the project, but years went by before he was able to secure funds to hollow out chambers and a tunnel within the 600-ft.-high cone of basalt cinders. "I've spent 36 years in the desert," he admits. "It attracts strange people and makes them stranger."

In person, Turrell seems as straightforward as his rancher attire. He resembles a slimmed-down Orson Welles, with his white spade beard, gleaming eyes, and husky voice, and he juggles smaller projects while Roden Crater inches toward completion. Like the architect Steven Holl, who was also raised as a Quaker and developed a passion for light, he designed a friends meeting house in the Oak Park district of Houston. He has created a score of skyspaces for private clients and museums around the world. Each comprises four walls and a cutaway roof that frames the sky. As visitors gaze up, the blue or gray of the sky intensifies. The most elaborate of these installations juts from a canyon in Beverly Hills. Five thousand LEDs and incandescent lights wash the walls and are computer-programmed to slowly change tone, which makes the square of sky appear to turn red or black—a convincing demonstration of how fallible our perceptions of color really are.

For the Benesse Art Preserve on Naoshima, an island in the Inland Sea of Japan, Turrell collaborated with architect Tadao Ando, who is himself a master of light and shadow. In their first joint project, the emphasis is on the absence of light. Ando constructed a black wooden barn with a series of baffles to separate the open entry from an inner room that appears, as you feel your way in, to be pitch dark. You sit, with a few others, on a bench against the rear wall until your eyes have adjusted to the gloom. After 10 minutes, you discern a faint glimmer at the far end of the space. As Turrell explains, "When the eyes are fully opened in a darkened room, light is experienced as touch. It inhabits space rather than illuminating surfaces—as one discovers in a plane before breaking out of a cloud where there is no horizon and no sense of gravity."

For Ando, this was an extreme manifestation of what he strives to achieve in all his buildings. Westerners (and most Japanese) have grown accustomed to spaces that are evenly lit, artificially or from expansive windows. And yet, all but the last few generations of humankind lived contently with small openings, lanterns, and candles. The book In Praise of Shadows was published in Japan in the 1920s as a protest against the onset of bland uniformity, and its arguments are still relevant. Ando creates architectural promenades—notably in the subterranean Chichu Museum on Naoshima—in which the alternation of bright light and deep shadows elicits a tactile response to textures, vistas, voids, and blank walls. There is a constant sense of discovery that draws you forward, and at the end of that promenade is a Turrell skyspace. The architecture has done its job of preparing you for an aesthetic and spiritual immersion.

Roden Crater will deepen that experience. About 1.2 million cubic yards of dirt were shifted to make the crater rim symmetrical. "The workers asked me what all this was about, and I told them that they were using their caterpillars to shape the sky," Turrell recalls. An 854-ft. tunnel slopes steeply up from the entry chamber to another, and a flight of steps ascends to an elliptical opening in the side of the crater. From there you can walk around or lie prone on a stone bench gazing up at the sky, which is framed by the rim of the crater and appears to be domed. Turrell likens the openings at either end of the tunnel to pinhole cameras. Once a year, at the solstice, the sun shines directly down the tunnel and appears as a projected image on a 15-ft.-high slab of white marble. Once every 18.6 years, the moon will cast its image on the opposite side of the stone through the entry portal. At night, when the interior is softy lit, the oculus at the end of the tunnel is black and the stars appear only when you've climbed to the top of the stairs.

Turrell is still fine-tuning his astronomical instrument and has stopped talking about an opening date. (It seemed almost complete when I was there in 2002, but I was obviously mistaken.) Eventually one small group at a time will be driven to the site, where they can sleep overnight in a lodge and spend hours absorbing the subtle shifts of light and the magical spirit of place, as you can do in the great cathedrals of Europe. Though the opportunities to experience this marvel firsthand are scant, and photos cannot capture the scale, Roden Crater is sure to become a touchstone for the shaping of architectural space.