This photo was taken in Bryant Park, Manhattan, New York City.
One of the park's most impressive features is, as you will have undersood, a large lawn that is the longest expanse of grass in Manhattan south of Central Park. Besides serving as a "lunchroom" for midtown office workers and a place of respite for tired pedestrians, the lawn also serves as the the seating area for some of the park's major events, such as the HBO/Bryant Park Summer Film Festival. The lawn's season since 2005 has lasted from shortly after the fall fashion shows in February until October, when it is closed to make way for The Pond, the park's ice skating rink. During the lawn's season, it is open on most days, closing only for regular maintenance, to drain after a heavy rain, or to recover after high-impact events.
They have probably mixed up the signs here... or the joke is quite funny !