Now THIS is interesting. Whereabouts can this be seen? Does anyone happen to have any photos? I'd totally love to check this out.
From the top deck of the Mark Twain facing forward, it's on the port (left) side after the Indian village and just before the abandoned mine train. It's covered up by lots of foilage. it's looks a bit like a footpath, but it is actually the remains of the pack mule trail. It's the only part of the area that's actually level.
Keep in mind that all this was true before the current refurb. With all the work they're doing over there it may be gone by now.