The Merchandise Mart is the world's largest commercial building, largest wholesale design center and one of Chicago's premier international business locations. Encompassing 4.2 million square feet, the Mart spans two entire city blocks and rises 25 stories. Opened in 1930 by Marshall Field & Company, the Mart is the largest trade center in the world and welcomes more than three million visitors each year, as it hosts trade shows, conferences, seminars and special events. Tours of the Merchandise Mart are available for the general public throughout the year for $10 for adults and $8 for students. For a schedule of upcoming tours, call 312.527.7762. But, kids will probably prefer the new bi-level mall built on the first two levels of the building, which is large enough to merit its own zip code!