C. asked: “What is that big green fence doing in City Hall plaza, near the subway? It’s been there for years.”

I’ve wondered too! Turns out inside the fence, which takes up a big area just south of the Brooklyn Bridge station on the east side of City Hall Park, are the skylights — glass bricks, if I remember correctly — for the subway station.

The MTA said erosion around the glass skylights has caused water leaks into the station, and the MTA will begin a construction project to replace those skylights with concrete starting next year.

The station is 120 years old, so during construction they are also going to rehabilitate the ventilator batteries, which have corroded over time and are due for upgrades to avoid water infiltration in the station. The whole project will likely be complete by 2028.

The current barricades around the skylights will likely come down earlier than that, but new barriers may come up at different locations during the three years of the project.