The massive 26-story Builder's Building once featured showrooms of construction materials and techniques. The original design, a limestone and terra cotta office building wrapped around a central Beaux-Arts style atrium, is fairly standard. But a curious 1986 renovation extended the building east along Wacker Drive. The addition added floors and a sloping glass wall resembling an oversized mansard roof. The building's tall, elegant lobby doubles as a space for events.