 Between the original and new buildings, where there was formerly a street, a wide street-level walkway connects the plaza on LaSalle Street to Van Buren Street in what would ordinarily be the building's first floor.Passing over the Van Buren Street elevated tracks, a green glass-enclosed steel-frame bridge connects the lower southwest corner of the 23 story addition to the Chicago Board Options Exchange (although this bridge was closed to pedestrian traffic in the wake of the September 11, 2001 attacks for security reasons).In 2005, the building underwent an extensive $20 million renovation directed by Chicago architect Gunny Harboe, whose restoration work included Loop landmarks the Rookery Building and Reliance Building.