Here's a wall shown to me by Frank Maykuth. It was interesting to me in particular because I grew up near it and I have a picture taken of me with my family when I was very small, standing within 20 yards of it.
It does not form an enclosure. It's one of those features, though, that I'm not certain about. It's probably just a field clearing wall built near the top of the Kittatinny for some reason, but the section below bears looking at.
To me the stone looks relatively new. The sandstone on the mountain is pink when cut or broken, and you can see pinkishness in the large stone. It does kind of look as if there had been a chamber of some kind here that was filled in, though, which is what Frank suggested.
Thought I'd put these pictures out there in case someone cared to comment.