Although the Northwestern Atrium Center (now Citigroup Center) meets the street as a cool, reflective waterfall of glass, this exuberant architectural rendering shows the building exploding from its foundations to expose the complex program of its base. Removed from its messy urban environment, the structure appears to float in an abstract grid, an example of Helmut Jahn’s creative exploration of the motifs, materials, and attitude of high-tech postmodern architecture. Unlike the heavy mechanics of other designers working in this vein, however, Jahn’s work evinces a touch of nostalgia for the delicate qualities of industrial architecture of the past. His Northwestern Center fuses a contemporary mirrored-glass facade with curves and articulation that recall Art Deco interiors and 19th-century iron-and-glass train sheds, an appropriate reference for this modern commuter train hub.