@glyn: my reference was to all zoos in general, but specifically concerning Taronga was my disappointment with the section of the zoo with the jungle cats and spider monkeys. The small cat display might be practical, but the enclosures should have been torn down by now. And it is enlightening to realize that the spider monkeys do well in their exhibit, but I stand by my initial description and it is a horrible little enclosure.
You bring up some good points on the heritage aspect of the zoo, and converting the old aviaries and seal pools would be a fantastic step for the collection. Any word on when construction on the South American section will begin? It's amazing how much money Taronga has already spent in the past decade...and is the South American section going to cost an astronomical amount?