What is it ??

[Borad]

Air filter?

 

[Ron Evers]

I looked up Chicago landmarks but that was no help.

 

[Heather Koch]

Nope, heres a less "zoomed" image...

 

[Heather Koch]

Heres it in color too

 

[Borad]

Doorway?

 

[Heather Koch]

Close, but I won't accept that as the answer lol...

 

[snowbear]

Close, but I won't accept that as the answer lol...

I'm not sure whom you are saying was close.
Is it some kind of a skylight on the roof of a building?

 

[Heather Koch]

To the doorway post.

Nope... Lol heres another image. This should make it easy...

 

[snowbear]

The "cover" (walls & roof) for a stairwell to/from the building roof? If there's another name, I don't know it.

 

[Heather Koch]

Thats it! I don't know the official name either, but that works!

 

[snowbear]

Yay . I'll post something in a little while.

 

[Borad]

I think it's called a hatch. I couldn't tell whether there was a vertical door or the diagonal hatch so I went with door.

 

[snowbear]

OK. I am looking for the name of the whole object, not just the part shown. Good luck.

 

[snowbear]

Nobody? I'll wait a few more hours then post a wider shot.

 

[Borad]

Nut driver?