Visiting old sites

I have been to a lot of rock pile sites, 524 by the last count, and it makes sense for many reasons to go back and look at some of them again, even though exploring for new sites is more fun. This summer there have been no free weekends for exploring and I finally broke down and went out at the end of a workday, to Spring Hill in Acton. To make a long story short and etc, I went back to a very obscure corner of their conservation land and looked for rectangular rock piles with hollows - that is what I am into these days. It may be a bit of a stretch but I think I found them. Before, I only saw a jumble of rocks. There is no surprise to it. Having a compulsion to see such things everywhere, it is apt when badly damaged structures leave a lot of room for the imagination. But bear with me, lets hear it as an anecdote.

Going in from the south along the Spring Hill Rd trail, I took the side loop to look at the rock pile grid. I am proud of what has been done there, the piles are beautiful, mysterious, and their structured layout is intriguing, if you look at it. A quick picture,
and I continued, past the old oak and its surrounding rock piles (hidden from view by saplings) down to the trail skirting the swamp.

It has been dry and I was thinking about cutting across the swamp to get to the site. So I gave it a try at the first opportunity. Well, the water wasn't the problem. It was the bullbriar/viburnum thicket in the middle that slowed me down. Sure it is fun getting scratched up and taking several seconds to work out each step but after five or so minutes it was over and I was back into ferns, and then rocks, and then rock piles.
As soon as you step into this place, things get weird. That little line of rocks to the left of the boulder suggest a structures with a (you guessed it) hollow, built against the boulder. This is one of the fashions of "Wachusett" pile, I first started seeing in Dunstable .

How about this?
That is a rock pile "with a tail", a form of hollow that usually occurs with badly smeared rock piles - suggesting this is an old style.

I walked around for 1/2 hour looking at things, trying to imagine I was seeing rock piles with hollows and then, as I swept back and forth in a more north easterly direction along this edge of the swamp, the character of things changed slightly and I was in an area of propped slabs:
Later, after that, I came to an area with lots of rock piles built up on boulders (the earlier ones were more smeared out ground piles).
More anon.

Meanwhile, I noticed how flat the land surface was, how the setting sun would graze the entire area making infinitely long shadows and speculated about that as the underlying reason for these piles to be here and not some other where. I posted that video to try to show it.

It looked like that, the sun was setting, I realized suddenly...