Yes, it is. The island has the gym area you can see behind Jock in the photo, plus the shelter (shown in one of my other photos) which they love to sit in. The food is thrown to them across the moat which is why Jock is sitting there in the photo. He had just scooped a lettuce from the edge of the water!!
They like the shelter because it has a roof and protects them from wind.
Otherwise the island is largely open and the Gorillas spend more time indoors, particularly the male Jock who only comes outdoors occassionally, principally at the feeding sessions. I believe he spends 98%(or thereabouts) of the rest of the time sitting indoors.