On the fringes of a favorite site in Tyngsboro

I have written before about this place. The main feature is an aperture pile with a hole pointed directly at a propped boulder. You can just make out the aperture in this pile. The next picture shows the boulder you can see through the aperture:
I turns out there are quite a lot of piles near the aperture - It is worth identifying the place as an individual site. Here are a couple of other nearby features:
And there was at least one more substantial pile (damaged).
This is Bruce McAleer. He noticed a large number of "pairs"at this site. I like this example: