Hawaii is no stranger to Wal-Mart: This idyll of rainforests and killer curls is already home to six of the big boxes. To break into downtown Honolulu, however, the house that Sam built had to think a little more vertically. Wal-Mart currently has a two-story project under, with a Sam's Club on top of a ground-level Wal-Mart, each with a 150,000-square-foot footprint. The building will include an extra 4,000 square feet for other tenants, as well as a four-story, 1,700-car garage. Building up isn't unusual, says Wal-Mart Design and Construction Manager Jerry Day, who finished a similar project in Baltimore last year. But only dense urban centers warrant them.