Rem Koolhaas had never done a store before Miuccia Prada approached him, but he had researched shopping while teaching at Harvard. His first foray into retail is a brainy roller coaster of a store with a precipitous dip, moving carriages of clothes and magic mirrors that let you see front and back at the same time. The dressing rooms alone, with glass doors that frost over at the touch of a button and a closet that transmits information about your chosen garment onto a screen, will make this a must-stop shop.