The best way to enjoy Manhattan is from Brooklyn. Transmitter Park offers views without the crowds, and you can pick up coffee-to-go and treats from nearby Ovenly. The India St/Greenpoint Ferry is a 5 minute walk and will take you all the way to the Rockaways in the Summertime.
The permanent piece called "Meeting" at MoMA PS1 is an etherial experience of light and color and quiet. Sit and look through the cutout in the ceiling and watch the light change both outside and in. You can't tell what you're looking at until maybe a bird flies by.