Yes, this is a Mies building - or maybe his son - in any event, very Mies.
Rusty - an interesting thought - to shoot all the time in overcast - but I'm not sure that I'd want to replace skies all the time, it adds quite a bit of time to the jobs. I did it on this rainy day - so maybe you are right;http://www.joshpabstphoto.com/burnham-center-before-and-after/
I will agree that balancing a super bright sky and deep shadows is a real challenge - and some amount of 'HDR' style technique is usually necessary.
For the most part, the tweaks were as you said - contrast - and usually when I have flat lighting, I will use a tad more 'clarity' in lightroom to compensate for the muddy nature of the lighting.
AJfofo - it's true that the perspective has been corrected - and if you don't use a tilt-S___-lens you will not have the vertical lines straight. That said, most
architectural photography has vertical lines straight - as I've shown.
I'm going to do more of these and talk about them on my blog in the category
architecture photogrpahy before and after