In the Illinois Center development, the main lanes of Columbus are on the middle level of a three-level structure. That level intersects with the middle levels of Randolph Street, Lake Street, South Water Street and Wacker Drive. All these streets also exist on the lower and upper levels, except for Lake, which is a pedestrian mall on the upper level; both of these levels go only from Randolph to Wacker. Ramps are connected directly to Columbus at the following points:
Southbound downramp and northbound upramp between the lower and middle levels, between Randolph and Lake; no access from the upramp to Lake
Westbound downramp and eastbound upramp in the middle of South Water between the lower and middle levels, just west of Columbus
Westbound upramp from the service (lowest) level at Wacker to middle Wacker west of Stetson Avenue (which quickly goes back down to become lower Wacker)
Columbus originally only went south from Monroe Street, south of Illinois Center. In 1980, it was extended to Wacker, including the three-level portion, and it was built over the Chicago River in 1982, connecting to Fairbanks Court. In 1992 the upper level of North Water was built.