I'm not sure that I've ever seen such an original barrier, and it is possible for an indivdual to touch the edge of the cement over the bars. It definitely allows for up-close viewing opportunities of the gigantic tortoises.
Is this is a converted exhibit? Almost looks like it might have had a large mammal in at some point (behind a concrete moat) and they've done a conversion job. Otherwise I don't see why you wouldn't just go for a low fence or glass window - nice though it is to see something a bit different.