Speaking of nice modern buildings that were badly updated:
http://www.emporis.com/application/?nav=image&id=108427
These three office buildings are located quite close to my home. I had my first
summer job in the middle one in 1981 (and again in 1982). They were built in
1964, finished with fairly good looking white bricks. What you see here is the
result of a facelift done in the late eighties as far as I can remember. In
addition to ruining the exterior, the architect in charge of the project had the
bright idea to remove a plaque inside the main hall of the leftmost tower
(the one with two wings), commemorating the official opening of the complex
by the mayor of Montreal, Jean Drapeau. I guess this was done so that
visitors would not get any evidence that the buildings were 'that old'.
P.S.: here is another modern picture, but I could not find any 'before' view.
http://www.flickr.com/photos/caribb/5216159992/