"Designing an artificial crater in the dunes of the Netherlands might have seemed like a daunting feat, but not for the master of light (and see below for Turrell’s most ambitious work yet within the Mother Nature–made Roden Crater). Built in 1996, James Turrell’s Celestial Vault is described not as a sculpture in the landscape, but as a tool to look at light and color. And this tool is expansive—30 meters wide and 40 meters long—creating an optical illusion of a domed sky."