One South Wacker is one of the few buildings along this stretch of Wacker Drive that has mercy on the Chicago River and the sea of humanity flowing past it. The building incorporates a number of setbacks to allow sunlight to penetrate into this bustling corner of the Loop. Still, in spite of the gaps created in its form, One South Wacker is still a very imposing presence in the neighborhood. From the ground, its angles create the appearance of a massive mountain of glass and steel looming overhead. Its windows are tinted in forms reminiscent of cathedral windows, adding additional verticality through optics rather than physics.