The Bronx Botanical Garden is a place my father and I have been going to since I was a child. Here's a photograph I took of him here. It has hundreds of species of trees and flowers. Sitting in the middle of the Bronx, it's most recognizable as a green oasis from the grays and concrete of city life.
Has no sign outside, so you might miss it, but if you do happen to find it, you will feel like you have walked into the 1920's. Its very chic, with Black and white marble decor, candle light and ambience to go with a great list of cocktails and whiskeys etc.