Looks unfamiliar and a little weird. Maybe it’s somehow connected to the vent system? Or it’s an unusual part of an eavestrough? It might be intended somehow for collecting water. Or a usual way to install skylights. For example, if you don’t have access to the roof but want some natural light in your apartment from above.
It seems to me that I have even seen something like this on the Internet. It was like a system of lenses that allowed you to transport the light inside through a tube.