I wish they'd make the rain forest so it doesn't smell so bad! It's AWFUL! It's too bad because it's a really nice exhibit. I've been to the rain forest in central park zoo and it doesn't smell bad like that. Maybe some air recirculates or something. I don't even go inside anymore because it smells so bad. Really like the zoo other than that.
The smell is basically all the animal urine, as the scat is cleaned up pretty quickly. When the building first opened, keepers thought the smell was bad as well, and decided to use air fresheners and sprays to fix the smell. However, the scent of the air fresheners irritated the animals and they urinated even more to overwhelm the smell. That's why they stopped using the fresheners. Once you visit the Rainforest frequently, the smell stops bothering you.