I believe that the pandas in Vienna have bred twice, in 2007 and 2010 (and all natural breeding as well). It is indeed a very nice exhibit and probably the best in Europe. I have only seen the other one in Berlin and not Madrid though so I am only judging by pictures here.
However, the exhibit in Vienna is well structured and now densely vegetated. The pandas can be seen both indoors and outdoors and the exhibit is split in two. I went this summer but unfortunately will post no pictures.
I have many pictures of this exhibit but I don't upload to ZooChat any more after The Great Photo Purge of 2010. I simply don't want to waste any more time on it.