As for the Zoo, notice that Berlin has two. Zoo in West Berlin, which seems rather tightly packed, and Zoologischer Garten in East Berlin, where there's more breathing space between the animals (and thus, farther to walk) - both have their advantages, I suppose, but I do prefer the east one.

Last time I was there, I saw a caretaker actually washing down the trash cans and wiping off the benches because it had been raining. Most of public places I go to in Berlin feel quite clean. Also, nothing like sending your kids off to play in the freshly raked
sand of a public playground. Sauber (clean in German)