If you drive over the Interstate 74 bridge, you drive right over the top of them. Columnist Barb Ickes has long been curious about the row of windows that are built into the underbelly of the bridge. So, she went looking for an answer. From 1935 to 1970, the bridge was a tollway. The concrete "plaza" in the middle of the twin spans formerly was the toll plaza. And to accommodate the toll takers' needs, offices were built into the concrete pier directly under the plaza. When the tolls had paid off the construction of both spans, the toll booths were removed, and the offices no longer were needed.