The Building is part of the underground pedway system connecting other downtown buildings as far south as Chase Plaza and as far east as the AON Center.  Additionally, 203 North LaSalle is connected to a pedestrian bridge across Clark Street, which links neighboring buildings to the east.  The Pedway is a safe, quick and convenient way for pedestrians to travel downtown - especially in the winter and during times of rain and snow.

http://www.cityofchicago.org/content/dam/city/depts/cdot/pedestrian/Pedway/PedwayMap2013.pdf