When he designed these residential towers at 860‑880 North Lake Shore Drive, Mies van der Rohe cemented his reputation as the master of Modernism. The building, a marvel in terms of its shape and proportions, was the first time the concept of the glass and steel curtain wall developed by the architect was used. He uses steel columns set in concrete to create a formidable vertical dynamic thanks to girders visible on the outside, between the windows.