Jardin Zoologico de Buenos Aires

Not sure why there's so much hate for this zoo. As an American and worldwide zoo aficionado this zoo is completely fantastic. Don't ask questions, just go. In fact, we loved this zoo so much that we went twice. Let me get this out of the way and just confirm what other reviewers have noted.
1. This place is fairly run down.
2. This place is pretty unsafe. You can touch most of the animals, and even some of the aggressive predators. I mean, they put a sign in Spanish that says these animals bite but as an adult with a moderately long arm span I could easily reach inside some of the cages. I think a small kid would be fine though. The other thing is that except for the really dangerous animals (like the tigers), they don't really believe in walls or cages; there's just a tiny wall that many of these animals could easily jump over and maul you. Plus one star just for that!

Now as others have mentioned, you're allowed many of the animals. In fact, they encourage it. You're supposed to buy their special food, but on multiple occasions I saw some of the locals feeding the animals all sorts of appropriate foods (like the small kid feeding the deer a ham and cheese sandwich, it doesn't get more natural that that!). As a result of all of this madness, there are two types of animals in this zoo.
1. Super happy and well fed animals that follow you around and do all sorts of stuff for food. Plus 5 stars for these guys!
2. Super unhappy, and possibly slightly crazy animals (twitchy elephant and pacing wildcat I'm looking at you). Minus one star here.

So to summarize, +1 star for the danger factor, +5 stars for the super fat well fed animals, -1 star for the crazy animals. Total score, 5 stars!!!!

If you are in BA, go here at least once. I'm fairly sure it's gonna get closed down soon, and you'll never see anything like it anywhere else.