I spent five hours on a train today travelling from Düsseldorf to Berlin. So I didn't get much time to see anything. Here's something I saw at Düsseldorf's K21 last year and again yesterday. Claudia Wieser's mural covering part of an arcade is a montage of photocopies from the book Alte Belgische Innenäume (1930) blown up to life size. The superposition of real and virtual architectural spaces in conflicting perspectives generates a feeling of vertigo. I would be interested in seeing more of her works, especially those interacting with architectural spaces.
Wieser at K21, Düsseldorf 2010: