The Okuno Building (1932) is of a rare vintage in ever-redeveloping Tokyo; most such buildings have long come down. But a concerted effort by artists and preservationists has kept it standing, and the seven floors of rooms filled with boutiques and gallery spaces (most open noon to 7pm, closed irregularly). Climb up and down the Escher-like staircases or use the antique elevator to explore.
If you'd like some direction, check Wakako Shibata's gallery Ishi (http://artgalleryishi.com) on the 2nd floor – she speaks English and French. On the ground floor look out for Makoto Optical (www.makotoweb.com) selling vintage and new spectacles, and Union Works shoe shop and repairs.