This is a pro tip, but also a summer tip, take the ferry from Lower Manhattan to Rockaway and spent the day. The beach is great and the area is impossible to gasp that it's 30 min from Manhattan (without traffic) - Eat as many tacos you can, cause it's the best in the state of New York!
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 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.