If you look closely at the very top of the lamppost, you might be able to make out two taut pieces of fishing line, one running toward the top and one toward the left side of the photo. They are part of the Manhattan Eruv, an eruv being a ritual enclosure in which observant Jews are allowed to carry things in public on Shabbat (the Sabbath), which would otherwise be forbidden. Eruvs are inspected regularly, and a break was found in the Manhattan Eruv a few months ago on a Friday afternoon, hours before the start of Shabbat, in an area near the United Nations where access was restricted because the UN General Assembly was meeting.
I took this photo at the intersection of 8th Avenue and 56th Street, looking north. All the maps I can find online show the eruv running straight along 56th Street here, but you can see in the photo that it turns south onto 8th Avenue. Perhaps it was recently altered to include a larger area?