Photo by myself, above Park Avenue on the Upper East Side.
What a view!? Notice that many penthouses have terraces full of trees and flowers. It's a nice luxury to live so high up and enjoy your own open space and garden.
I always associated Park Avenue with limestone, but as you can see, there is a lot of brick on this street, too. Park Avenue distinguishes itself for a planted divider that separates traffic in each direction. At the moment, purple tulips and leafy trees are in full bloom.
Also, unlike many north-south avenues, Park Avenue north of Midtown is completely residential. No bodegas, no boutiques, no supermarkets. The benefit of this is that there are no distracting signs or lights at night. The drawback, of course, is that you can't just run to the corner store for a gallon of milk.
There are other purely residential avenues in Manhattan, including West End Avenue, Riverside Drive, Columbus Avenue and Fifth Avenue.
Related posts: The View from on High, High Above Bryant Park and The World Above Central Park.