@Baldur: seeing all of these photos from your American zoo tour is fabulous, but it is also somewhat discouraging to see countless bear grottoes from the Cincinnati, Cleveland and Detroit zoos. These cement/gunite/rock enclosures are all badly outdated and in some cases more than 80 years old. Note to zoos: TEAR THEM DOWN! There are plenty of superb bear exhibits in North American zoos that are naturalistic and modern, and yet there are probably over a hundred grottoes packed with pacing, bored bruins.
I would agree with you about many of the old American grottos, Snowleopard, especially those in Cleveland and Cincinnati. Those in Detroit are somewhat larger, but if they can do as good job for the Black and Brown Bears in Detroit as they did for the Polar Bears, then it would be great. But, honestly, I have seen such bad bear exhibits in zoos all over the world that many of the American ones almost look modern in comparison.