Throughout Europe, the Spanish engineer-architect Santiago Calatrava is famous for elegant bridges and public buildings that are descendants, in their different ways, of London's 19th century steel-and-glass Crystal Palace, the greenhouse-exhibition space that signaled the beginning of pure engineering as the new form of beauty. For his first completed work in the U.S., Calatrava provided a showstopping new addition for the Milwaukee Museum of Art. His low-slung extension is crowned by a supreme statement, the upward arc of his brise de soleil. It's a sunscreen with "wings" made of 72 steel-pipe ribs. They rise and fall from a diagonal spine like a bird on an ascending flight path. Technically, Calatrava's great wings are functional when closed they shield the museum's arching skylight. In fact, their real function is pure glorious gesture, a flourish of structural brio. When opened their lovely wingspan gives the museum a stratospheric silhouette and Milwaukee a stunning new landmark.