You know as much as I do, as the exhibit is wonderfully designed and it is difficult to figure out where it begins and ends. That huge rock to the right might conceal some concrete platform or it might simply be a large stone. The grizzly brothers each weigh between 850-900 pounds, and that gives an indication of the size of the rocks in the habitat.
The big artificial rock serves a few purposes: it blocks cross views of people from different viewing locations; it acts as a "lookout" for the bears; and it contains a concrete bunker that was to have served as a shelter for red foxes, accessed by various small tunnels. The red fox were never introduced to the exhibit, so the bunker has never been used.
Tho rock is right at the edge of the barrier moat, so when bears are on it they appear very close--because the moat is so well hidden by plantings and landforms. Brilliant
Brilliant landscape immersion exhibit! It is virtually impossible to see any fences, moats, grottoes, wire, poles, etc in this award-winning grizzly bear habitat. An intelligent individual can guess where the hidden barriers are, but if I had a dime for every time a zoo visitor asked the question "where is the fence" or "can't the bears get out of there" then I'd be an extremely rich man indeed. There are at least 5 viewing opportunities for this enclosure, including a large underwater window and a cave that allows for humans to be within a couple of inches of the 850 pound bears.