The enclosure for the pair of hooting and hollering siamangs is not as large as it appears in my many photos of it in the ZooChat gallery, as there is a dense forest that is behind the exhibit and not completely inside the ape island. However, the habitat is still outstanding, and on sunny days the apes are often at the top of the tall trees.
@Ituri: it is impossible to determine where the siamang island begins and ends, and your description is appropriate. This is really a wonderful exhibit, and so much better than the vast majority of gibbon enclosures at many other zoos.