I think this was the second tank. The first one, you kind of just walk up to. After that each one gets exponentially more difficult.
See what I mean? This is only the second tank!
ok, ok, you caught me. It was more like this...
You can still see the iron bar sticking out of the rock in the background. I thought it would make a funny picture. We pondered a little over what it might have been used for and neither of us came up with anything good.