The Chelsea Market is filled with great restaurants and speciality food stores and pop up shops. I love stopping in and getting a gourmet grilled cheese from Lucy's Whey or a healthy juice from raw food restaurant One Lucky Duck, while shopping for dinner ingredients at the Italian market Buon Italia. For a great sit down restaurant, I love The Green Table, which serves great farm to table food.
My favorite restaurant to pop in spontaneously on a weeknight. Get the lamb burger with sardines and a mezcal negroni. It also has my favorite looking bathroom in NYC.
My second-favorite outdoor-place in Manhattan. The abandoned 1.6 km rail tracks running above Chelsea down to the Meatpacking district were turned into an above-ground park. Perfectly nice place for sitting in the sun, reading, relaxing, having lunch in some green spot in the city. Nice views at the Hudson River, New Jersey, the Statue of Liberty (little small from there but still visible) and the architecture around Chelsea.
The Franklin D. Roosevelt Four Freedoms Park is a four-acre memorial to Franklin D. Roosevelt designed by Louis Kahn that celebrates the Four Freedoms Roosevelt articulated in his 1941 State of the Union address.