The expansive (4.2-million square feet, to be exact) center houses everything from casual furnishings to a kitchen and bath center. Spanning two city blocks and rising 25 stories, it's the world's largest commercial building as well as the largest wholesale design center. Over half of the building is made up of wholesale showrooms, but it also houses several major trade shows, conferences and seminars every year. What's more, the Mart features LuxeHome, "the world's largest collection of luxury boutiques for home building and renovation," as well as a number of retail stores.