The Frank Stella’s are the best. They are all over the city and they always look amazing. Two of my favorites are the Saatchi and Saatchi lobby (pictured) and the Citi Corp building in Midtown.
The rooftop garden at the Metropolitan Museum of Art. The museum floors below are a maze of tremendous art and inspiration, and taking the elevator to the rooftop garden is the icing on the cake. 360' views of verdant green Central Park bordered by cool glass and steel of Manhattan's cityscape in the distance.
Luhring Augustine did a good job of converting an old warehouse/storage facility into a blue chip commercial art gallery that stages four shows of contemporary art per year. Which means you can catch museum quality shows in an unlikely spot, away from all the Chelsea pomp, and it actually has friendly staff, instead of a cold gallerina sat behind a desk pretending to be on the phone.
I love sneaking over here in the middle of the day to see a movie - they always have the best selection of films. I recently saw Pina in 3D and The Kid with a Bike here, and another time I saw Bela Fleck play the banjo after a screening of Throw Down Your Heart.