The world's largest commercial building, the Merchandise Mart (built in 1931) encompasses approximately 4.2 million square feet, 6 million if you count the Chicago Apparel Center across the street (the buildings are joined by an enclosed walkway over Orleans St.). Its upper floors house offices and designers' showrooms (furniture, office products, giftware) and are mostly not open to the general public. The first two floors, though, have been turned into a retail mall (stores include The Limited, Coconuts Music and Movies, Crabtree & Evelyn, Coach, Episode and H20, among many others). There's also a bank, a food court, a well-run post office branch and stirring Art Deco interior architecture to admire. CTA elevated trains stop right at the Mart; the station is inside the building, at the east end of the second floor. Tours can be arranged through Tours at the Mart.