This broad, tree-lined boulevard is lined with boutiques from the top European fashion houses. More interesting are the buildings themselves, designed by some of the biggest names in Japanese architecture. There's no better (or more convenient) place to gain an overview of Japan's current sense of design. Highlights include the Dior boutique by SANAA (Nishizawa Ryue and Sejima Kazuyo) and the Tod's boutique by Itō Toyō.
Perhaps surprisingly, Omote-sandō was originally designed as the official approach to Meiji-jingū; that's why it's unusually straight and wide (as far as Tokyo streets go).