Yes my friends, I know the top window is opaque in the GOUT, but that circle shadow does not correspond to it. If you follow the slanted direction of the light source, that mysterious shadow would be elliptical not round, and it would be projected on the floor... what's more, the bars' shadow end abruptely sharp on the circle shadow while they should end with rounded joints (as the bars are clearly built that way).

I don't know what that round shadow shape may be, but definitively it is not an opaque top window :-)