What is it? This little round opening is in the wall surrounding the doors to City Hall.

My first thought was that it was for newspapers… but upon another instant’s reflection, all sorts of ideas came to mind. For the rats to escape … for snakes to enter since they cannot pull the door handle … for when they need to hose down the place because the BS is too deep … for injecting tear gas … for super high tides once in a blue moon … ceremonial entrance for Topo Gigio.

Ah, those were fond thoughts for about 30 seconds.

I suspect it is just a vent to equalize the air pressure on each side of the airlock doors.