The High Line is Manhattan's newest park, built on a section of the former elevated freight railroad along the lower west side of Manhattan.
When I was there in mid-April, I saw lots of families out for a Sunday stroll. The design of the park is very innovative, including what looked to me like oversize chaise lounges on flanged wheels set on areas of renovated track.
There are great views of New Jersey, just across the Hudson River, as well as the many buildings that border the High Line.
As of now, the High Line runs through the old Meatpacking District, from Gansevoort Street to about 23rd Street. Eventually, it will continue through Chelsea and terminate at West Side Yard in the lower 30's.