Haha, okay so I'm wondering what that woodwork the person is standing on is called. I thought at first it might be pillars or posts? Anyways I need to be sure, this is not necessarily needed for my book (but how can I know what I need if I don't even know the word?), anyways...when I'm stuck on something I won't let it go. It could be seen as some sort of banister as well, couldn't it? I really have no idea. Let's say you're supposed to describe the scene, more specifically what the person is standing on.
The first thought I had was that it could be described as a fort of some kind. I'm not sure whether there's a specific name for it though. http://en.wikipedia.org/wiki/Medieval_fortification Other than that it could just be described as a wooden walkway. I googled 'wooden walkway' and it brought up similar pictures to the one you posted. Also found something on 'battlements' so google that and see if anything comes up