Seen near Stuart Pond, Sterling MA. I did find a small site a few hundred yards away in similar topography. Although at first I thought this was probably agrarian, in retrospect it might actually be legit as an ancient rock pile. What I am seeing is, aside from the rock in the left foreground, a rectangular outline of larger cobbles with a few smaller ones on top. The foreground rock that we ignored is about the same size or a bit bigger than the "outline" rocks behind it.