The Merchandise Mart is the world's largest commercial center, and largest wholesale design center. The enormous property is 4.2 million square feet and acts as one of Chicago's premier international business locations. The upper levels of office space, designer showrooms and conference center space are closed to the general public. The first two floors, however, have been converted into a full retail mall that includes a post office and a food court. For guided tour information, call Tours at the Mart +1 312 644 4664.