Sunday, I went back to Sudbury State Forest (click here) and followed a trail out to a side I hadn't seen. Along the path I could make out a parallel stone wall behind 20 yards of pine saplings, and decided I had to follow the wall, off the trail. There in the corner, with suburban houses across the way, was this pile: The stick coming out of the pile is starting from a little hollow on the far side of the pile. Here it is from the other side after I removed the stick: You can see a little hollow there perhaps 2 feet across. I would be willing to agree that this is a deliberate designed feature rather than vandalism. There are no loose rocks around and it is easy to imagine someone sitting there and facing outward, in this case to the west.
Here is a closeup of the hollow:The red rocks might be significant.
This pile was placed a few yards within the corner of some stone walls. The stone wall was at the edge of the swamp and beyond the wall there was a little ground disturbance that turned out to be an elongated section of cobbles - not really a mound, not cleanly defined to my eyes: In this picture there are cobbles all the way from the visible ones in the foreground to the tree in the mid-ground. Beyond that the swamp. Let's take one more look at that little pile with a hollow:I like the look of it with the moss. In this last view we are looking towards the stone wall. The large rock there and that formless group of cobbles beyond suggest that there is actually a site here, not just an isolated pile.