I was just looking at Google Earth and there was nothing there but a pile of logs just like in the photo above. Maybe you should ask about what was there even before the panda wall went up.
Good to see them finally making use of this wasted space in a prime location in the middle of the zoo. Why it was unutilized for so long was always a puzzle to me. An even bigger puzzle is why they didn't use it to make the small panda exhibits bigger from the beginning.