About the Tierpark Berlin, I find it amazing how a zoo with so much space build so small exhibits for many animals. They stand in sharp contrast to the huge outside paddocks for animals like bactrian and dromedary camels.
I'm coming a little late to this discussion, but feel I should add my thoughts...
I pretty much agree with all that Sun Wukong says above. Yes, this is the poorest part of the Tierpark, and I would struggle to defend it in a zoo which, on the whole, I really do like very much indeed. But would it seem so much like a 'prison' if it had glass rather than bars at the front? If it was set in an immersion 'habitat' with lots of tropical plants around it? If it looked a bit more Asian? Probably not. And yet those changes would not alter the life of the bears one little bit. I'm not sure that many people genuinely undertsand the concept of freedom and liberty - let alone any animals. To talk in terms of prisons is understandable, but not, I feel, wholly appropriate.
The Tierpark does have its dodgy areas. I love the carnivore house, but I appreciate that some would take umbrage with it. Likewise the enormous elephant house. But if you want to be immersed in zoology, there is no better place to be (apart, maybe, from the Berlin Zoo).