You can see some good mash-ups here, here, and here. And creepy ones of the Altes here. They've done a really good job of matching the angles.
I thought I'd add a few to the online collection. So here are my attempts, matching my travel photos with ones plucked out of history:
|The Reichstag, during winter 1945 and spring 2015|
|Soviet troops storm the Reichstag in 1945. Merged with the idyll of 2015.|
|The Dome Cathedral, from across the Lustgarten|
|A mess in front of the Reichstag|
|Looking at the Altes Museum|
|Tooling around the Lustgarten with artillery|