Pneumatic dreams hover over the work of Tomás Saraceno, just as they wafted through the hot-air balloons of the frères Montgolfier or the late-1960s inflatable architecture of the Utopie group. But if it seems that all we got from such techno-futurism was puffy IKEA chairs, Saraceno won’t let the bubble burst. His airborne structures and blow-up sculptures are actually prototypes for floating gardens or houses. Such constructions—along with photographs, drawings, and a new installation for the Walker’s terrace—are the focus of “Lighter than Air,” the artist's second solo US museum show (the first being at the Berkeley Art Museum/Pacific Film Archive in 2007). Other pieces in the exhibition, such as 59 steps to be on air by sun power/Do it yourself, 2003, a set of simple instructions for making a solar-powered balloon, are more Mad Max than Bucky Fuller—rerouting utopian fantasies rather than merely fulfilling them.