where I walk with my dog near my apartment, is also the remains of what was Fort Putnam in the late 1700’s and later Fort Washington near the Navy Yard. Not the largest park but a regular part of my routine and big enough to feel like you’re still out of the city when you’re in the middle of it.
Summertime in Bushwick, means the locals will be barbecuing on the sidewalk, and playing in the hydrants. It's the perfect time to grab some shorts, and run down the street. If the one outside Mckibben isnt going off, one of the other 15 hydrants in the neighborhood will be.
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.