Immolate, that is some good looking stuff. I'm not sure what your motive was but since you put it that way I'm thinking this is a test, LOL...like I'm supposed to find the hidden picture.
Anyway, the only thing I noticed right off was that I see flags in the shadows but nothing in the positions on top of the towers. I suppose it's possible that they are so thin from my birds eye view that I wouldn't see them but since they are so fat in the shadow I'm thinking not. Far as the shadows go the only one that looks a little funny is the upper right tower's. Only reason is because the flag shadow just manages to hit perfectly on the top of the wall which seems almost too coincidental. I'm not likely to sit here and try to do the math so I leave that up to you. Again, I say the whole thing looks wonderful and I look forward to seeing updates.
I imagine you have to ask yourself if it's worth it to make things that real or not. An extra couple hours for each building's shadows seems like a lot of work. I'm thinking there must be some software out there that already does this for architects and whatnot. Might be better to get a second job with those "shadow hours" and buy it I know, labor of love.