In Shrewsbury before the heavy snow

Went for a nice walk in the area southwest of Centech Blvd in Shrewsbury. At (a) I found a low rock pile, hard to make out under the snow:

 It has some shape:

From further away:

Walked around a bit and came to an interesting enclosure on the side of a ridge near (b):

Big enough to sleep in. Facing roughly 145 magnetic.

Then I was following a wall, almost back to the road across from Fortune Dr. at (c) and saw the neatest little rectangular mound with a hollow to the right of the wall:

Closer:

This is a miniaturized version of what I see near Fitchburg. A pygmy pyramid.

 Looking back towards the pile, more or less south, along the wall - the pile is on the left.

Not a bad collection of finds in the snow and in a small woodland.

After that, I drove back along Rt 20 towards Rt 9 and what looked like an interesting bit of hill and woods I saw earlier. This turns out to be the part of Boston Hill north of the YMCA, a smaller summit. There I saw a couple piles next to a wall:

And a "kids fort" next to the playing fields at the top:

I am suspicious:

Then, on the northwest facing part of this northern summit of Boston Hill there were several similar structures that looked like small seats:

 Looking back from a second toward the first:

 Another view of second:

 Maybe a third one?