Coming up to a rock pile site (Harvard, MA)

(I really have to do some blogging.) Picking up from my last post, I went into a conservation land off Brown Rd in the Harvard/Bolton area west of 495. That western bank of Beaver Brook is one big extended rock pile site and there was this one little bit of swamp and hillock, adjacent to and visible from the highway, that I knew I had not figured out how to get to. So on my way home from a disappointing walk down in Bolton, I decided to try harder to figure out how to get there and, in the end went in the conservation land entrance on Brown Rd and then hung a sharp right to go down along the edge of the conservation land behind the houses there. I thought there must be something to see since there are so many rock piles in the general vicinity. So sure enough, as soon as I got to unexplored territory, heading further downhill, I started seeing new rock piles at a low density. In fact there were several entire knolls down there and more to explore than I realized. Here is a little pile next to the beginning of a brook.This gives you an idea about how recently people were in here building rock piles. But my guess is that this Beaver Brook/Elizabeth Brook watershed divide has always been a highway and always been an important area to the Native Americans. Here in Harvard, Boxborough, Bolton the Indians must have been living or at least visiting until quite recently. [Interestingly there is no such recent activity in many places, so I figure this tells us about Indians in the historic period.]
I cannot remember the context of this one, it was at the foot of the slope getting down to the swampy area. Proceeding further I came to water in a place that matched my impression of the swamp next to the highway. Looking across the water there was a little island.

The water here is standing water backed up by a beaver dam.
As I looked across (longingly) at this island I could see what looked like two rock piles out there - one to the right behind the large fallen down tree, the other to the left at the highpoint.

So I started across the beaver dam but I was pretty sure I would fall off into the water, so I took the picture and then reversed course, disappointed. Then I followed the edge of the water back aways and my disappointment started to ease after seeing this (there are 7 piles in the picture):