Why does Chicago's River City, an unusual cast-in-place concrete building, look the way it does? The answer is in Architect Bertrand Goldberg's philosophy on urbanism, building design, and people. Goldberg believes architecture can influence behavior. It can be friendly instead of aloof. He also thinks it can be structural. Architectural form that creates space doesn't have to be separated from the structure that supports it. Curvilinear concrete shells are both friendly and structural. The spaces they produce are lively, and because of the repetitious use of formwork, they're economical to build.

Since 1962 when Goldberg built the famous "corncob" towers of Marina City, he has wanted to build a bigger and better city within a city. River City is the result. Two parallel S-shaped residential towers separated by a glass-covered atrium sit atop a rectilinear base. Located in the South Loop of Chicago along the east bank of the Chicago River, River City puts one of the world's largest cities at its residents' doorstep.

All concrete in River City has a structural function. The concrete that defines the shapes of the rooms also provides the building's structural support. Each S-shaped building is created by a series of vertical concrete tubes (or pods) spaced at intervals along an S-shaped line made from two semicircles. A single column halfway between neighboring tubes helps support the floor slabs the span between them.