Go for a stroll

The High Line is a 1.45 mile-long (about 2.3km) the only elevated train track turned urban park in the Meatpacking District in 2009. It runs from Hudson Yards to the northern edge of Chelsea, and their architecture, plant design, and the view makes it one of the popular destinations in the Summer.
I recommend starting at the Hudson Yards and walk south to Chelsea so you can stop by at the Chelsea Market when you want to take a break from walking. Chelsea Market has a food hall  (there are many food vendors to choose from!) and a shopping mall.