Midtown is more than just skyscrapers and office buildings. Case in point: Greenacre Park. Located on 51st Street between 2nd and 3rd Avenue, this 60-foot-wide by 12-foot-deep shaded oasis offers a refuge from the chaos and, come summer, the scorching sun. Plus, the 25-foot waterfall is by far the most soothing scenery you’ll find within walking distance of your cubicle. These are the practically secret national parks you’ll want to visit this spring.