Classic Rock Pile with hollow

This is across Burroughs Rd from the northernmost entrance to Wolf Swap cons. land in Boxborough. You cannot miss it, but I almost did and came up from a different direction, spotting this pile for the first time, though I visited and blogged about the site previously (click here). Seeing this new pile clarifies the situation. Although the main pile I found was so smeared out no conclusions were possible, this time with the nice example above it became clear these are part of a tradition I have been calling the "Wachusett Tradition". There were the two mounds: the one above (here is another view)
and the one I saw before:There were also several smaller rock piles nearby. I cannot tell if these are from the same time period or if perhaps they were added by people who came later and felt the place was special. For one, these small piles lay along a curve that joined the two larger mounds:
How about these outliers:These are more or less traditional, rectangular marker piles. They seem less damaged, but who knows? So, nothing too intelligent to say about this site. I was accosted by the landowner (he was not sure which 3 acres he owned, and was wondering about the missing man).

Actually I want to make one (hopefully slightly intelligent) observation: this site is about 50 yards south of Rt 111, also called "Mass Ave" in some places, and a very old trail indeed. This supports my sense that these large mound sites are near old trails, suggesting there is a basis for thinking sites are not so often out in the middle of nowhere - if one includes the old trails as well as the modern roads.