Norman Foster’s original proposal for the Reichstag.
It covers 100 projects which, as you guessed, failed to get built in Berlin in the twentieth century, ranging from the very well known (Mies’ skyscraper on Friedrichstrasse) to the less so (Peter Cook, once of Archigram, happily wittering about some wonderfully odd plans for the western end of Kudamm).
The projects perhaps tell as much about the history of Berlin and of modern architecture as much as what was actually built – the megalomania of Speer, the almost-as-mad 1960s project to build a colossal motorway interchange by demolishing much of Kreuzberg, and the arguments and proposals over the big post-wall sites such as Potzdamerplatz.
There’s an extremely enticing book to go with it, which I’ll try and do a review of soon.
German text only by the way, with the odd english speaking architect in the interview videos (actually, pretty much all the interviewees are pretty odd, not least of all Peter Cook, bless ‘im).