I heartily recommend Ryszard Kapuscinski's 'Imperium' (it's available in English) if you want to learn more about the Soviet Union in general and different cultures inhabiting it at the time. A lot of spot-on analysis of how the system worked. Brilliant documentary writing, too.
Communist architecture followed the principles of communist architecture. Diversion from what the state thought was a good idea was highly un-recommended. The principles of communist architecture started off from a lot of high-minded platitudes about equality and national purpose, but in practice always translated to a monstrous block of filthy grey concrete with tiny windows that looks awful from a distance and only gets worse as you get closer.
It wasn't confined to the eastern bloc either, you can find plenty of horrible examples of a similar style dreamed up by western architects infected by similar principles; pretty much anything ugly, grey, concrete, and mid-century. They continue to blight our cities and (especially) our university campuses. But reconstruct a whole city in the same milieu, and you'll have Warsaw.
http://en.wikipedia.org/wiki/Konigsberg_Castle
. . . where they replaced a pretty castle with something like you describe.
Like, say, http://en.wikipedia.org/wiki/UTS_Tower ?
(To be fair, it's pebblecrete.)