habitats

I have not gone too many zoos but I am still fascinated with them mostly just since I like animals, in my opinion I think that the sand hill crane habitat in the Detroit zoo is a little disappointing, its not that its bad but it seems like a little of a case of less quality in it due to less...

I am wondering what are some of the best exhibits (for both animals and visitors) you have seen relative to the amount of money spent to build and maintain them? In other words, who appears to have received the "biggest bang for their buck," as we like to say in these parts? :)