This is the end that housed orangutans and then mandrills. You can make out the base of a wall to the left of the middle of the photo - I guess this was the outer wall with the outdoor cage being to the left of it. Half-way down the right of the photo is a step which presumably marked the limit of the indoor accommodation. That area is painted green - there is some green rubble piled up beside it.
The remains of the Winter Quarters are in the background.
