This link got a wow from me when I found it a few days ago. This guy has taken various Soviet Second World War photographs from eastern front city locations (Moscow, Leningrad/St Petersburg, Berlin, Vienna, Prague etc), figured out the exact places they were taken, then blended them with freshly shot images from the same perspectives:
Linky Page 1,
The page text is mostly in Russian (I think), but the images speak for themselves. I have seen many ‘then and now’ comparison photographs before, but few as skillfully realised as these (exactly reproducing the perspective and angles of an existing photograph is trickier than it first appears). Very impressive and one of the best removals of abstraction from history I have seen.