Right behind the prairie dog exhibit. You probably didn't see it because you didn't take the tram and it's in that location when you get off it to return.
@snowleopard - when I was there in 2005 there were two routes that you could choose to get down to the new part of the zoo. The one on the left, which you took, was some empty large grassy hoofstock yards (which seemed perfectly fine to me - not sure why they abandoned them). The route straight through the entrance had old cages and moats with boards placed in front to block the views. This cage may be there or it may be somewhere else. That route may have been completely closed after my visit?
