The enclosure seemed, to me, to have a great deal of glass viewing, which some studies have shown causes stress in captive Gorillas.
This article on Captive Gorillas in Germany, although a couple of years old, is really interesting with regard to types of Gorilla exhibit:
Gorillas in Germany - a review on the last ten years and an outlook to the future
Yes, I've read Olaf Paterok's article a number of times- you'll note he says Gorillas need a ROOF over their heads to feel comfortable.. and he's very right.
Too many enclosures nowadays(Bristol, London Paignton,Blackpool, Belfast and many in Europe) are designed as large open grassy enclosures or islands, usually without much overhead cover, plus an indoor viewing area only a fraction of the size of the outdoors. If allowed to choose, the gorillas prefer to stay inside except when tempted out by public ' talk and feed' sessions.
Sometimes the reluctance to venture outdoors is almost 100%
London's new 'Kingdom' has the same pitfall- the 'dayroom' is a small fraction of the total space, yet I'm sure given the choice, the gorillas will use it out of preference to the outside. When I went the other day, the new female Effie, was shut outside and she just stayed very close to the door, wanting to get inside again. When I went back later, she was indoors and Bongo/Bobby and Zaire were shut outside instead. Bobby went back and forth from the door to the cave and back again to sit near the door- just waiting for it to be opened so he could go back in again... My guess is once they are a group, they will be allowed 'free choice', resulting in less use of the outdoor island.
I think Glass Windows do increase stress levels, especially with nervous or excitable males (Port Lympne's Djala in the Palace of Apes enclosure is a good example.) At London the glass viewing is very nicely done I thought. Fortunately Bongo(his proper name...) is a relatively placid male and didn't seem at all perturbed by the nearness of the visitors or the glass. It does seem a bit pointless constructing enclosures with glass viewing and then later covering it with camouflaged netting as a stress relief. This could happen in future at London too but it will make viewing the animals for large numbers of people, far less easy.
Regarding breeding. They remain confident Bongo and Effie from Berlin/Leipzig will breed. I more doubtful though I hope so too as he is a wild caught male with no offspring. But he has a very poor track record and I'm not sure how socially normal he is having been brought up in an Italian circus. What I can't actually establish is if he mates with either female. They also say that Zaire is now too old to breed, this is rubbish - she's only 33 and her ex-companion Salome(31) now at Bristol Zoo had a baby in December.