This really appears interesting, as mweb08's pictures clearly show. Here's a video: Philadelphia Zoo Treetop Trail‏ - YouTube Reminiscent of London's http://www.zoochat.com/43/gorilla-kingdom-viewing-area-86123/ I seem to recall that we've seen pictures posted of other similar arrangements in European zoos
Oh, I thought it is for human children playing. There are many such rope trials or tree villages in European zoos and parks. A bit similar, Wroclaw zoo just build overhead pathway for black howler monkeys. They walk on a suspended ladder to an old pear tree. They lower trunk of the tree is protected by electric wire, like orangutan climbing apparatus in Rhenen.
Yes, this is a very nice addition to the zoo. I didn't get to see it in use, but hopefully I will during my next visit. The zoo has really made some positive strides with their last few major additions: Big Cat Falls, McNeil Avian Center, and now Treetop Trail.
It didn't really work out with the monkeys at London and access to the gorilla island was taken away.