While tinkering a bit at the back, I ended up at eye level with this fellow. Thought he looked a bit odd, with his wide opening fully exposed. Doesn't he look more decent with a hat on? Something that could have blown away? Now both sky juice and birds have free access.
The pipe in question goes into the boiler room, down into the concrete slab. I have the impression that it's some kind of ventilation? Perhaps for the sewer.
Anyway, does it look like something is missing?