I would guess multiple projectors, an accurate 3d model of the building and skillful art direction. You project a video-textured model of the building over the real building.<p>There were some other videos of similar installations floating around the web and they looked quite well even with somehow different viewing angles.<p>For example, here are some with quite large camera pans:<p><a href="http://www.youtube.com/watch?v=X85A1dCpzsI" rel="nofollow">http://www.youtube.com/watch?v=X85A1dCpzsI</a><p><a href="http://www.youtube.com/watch?v=3h3D6dCLAeo" rel="nofollow">http://www.youtube.com/watch?v=3h3D6dCLAeo</a><p>People are hardwired to see "3D" based on perspective / shadow hints in 2D images.