I just finished an article in Smithsonian Magazine about artist James Turrell and his 30 year Roden Crater project. He is erecting a concrete observatory, a "temple of light" at the bottom of a volcanic crater bowl in Arizona. The pictures are incredible. Turrell's tools are light, human perception, and precise mathematics. The Henry Art Gallery in Seattle is currently showing the exhibit, James Turrell: Knowing Light. The website of his last exhibition in Pittsburgh has some great visuals of Turrell's work.

The Roden Crater project is not scheduled to open until sometime after 2005. I plan on visiting.