One of the most famous shopping streets in America is Fifth Avenue. This posh avenue is home to many top designers and their flagship stores. Cartier, Tiffany, Bergdorf Goodman, and the Apple store... these are just to name a few of all the stores located on Fifth Avenue.
If you're not interested in shopping, you can still take a walk along the Avenue to enjoy the architectural masterpieces and the lights (especially in the evening).
The best area for promenade is from the south end of Central Park to the New York Public Library, or more specifically, between 60th Street and 40th Street.