Now that architecture is practically as glamorously daredevil as bullfighting, every year has its Most Anticipated Building. In 2006 there were two—Daniel Libeskind's addition to the Denver Art Museum and Norman Foster's Hearst Tower in New York City. This year, just one: the Bloch Building, Steven Holl's addition to the Nelson-Atkins Museum of Art in Kansas City, Missouri, which opens in June. It's going to be the year's most visible building on the strength of being the building that's not there.

Holl gave the Nelson-Atkins 15,000 sq m of new space by burying the space underground. (Architects love metaphors. Is this a reminder that all art traces back to cave paintings?) What appears aboveground are five irregular glass pavilions, transparent in some parts and translucent in others, which serve as vaulted glass ceilings for the galleries below while carrying out a kind of photon hydraulics. During the day they'll pour (diffused) light into the galleries. After dark, lit from within, they'll pump it back against the night sky. Call them lenses—Holl's term—or lanterns. They're illuminating.