Big retail is having a big week. Guess launches its largest U.S. store yet, on Fifth Avenue, this Thursday. The 13,000-square-foot, two-story monolith goes for the club look with chain-draped chandeliers, a patchwork rug stitched from over 500 vintage jeans pockets, and a twelve-foot LED screen looping runway-show footage. The full men’s, women’s, and accessories lines will be stocked (575 Fifth Ave., at 47th St.; 212-922-9792). In the West Village, Nars unveils its first-ever freestanding boutique, displaying lipsticks and palettes among illuminated floor-to-ceiling mirrors (413 Bleecker St., nr. Bank St.; 646-459-2323). Scoop-like Canadian fashion house Aritzia introduces its eight in-house brands (524 Broadway, at Spring St., third fl.; 212-334-3255). And the long-shrouded Alexander Wang store finally bows on Thursday, showcasing the designer’s much-discussed all-white spring collection plus his cult accessories (103 Grand St., at Mercer St.; 212-977-9683).