It's just at the peak of a steep stone outcrop and comfortably fits one person.
A theoretical problem is that the topo lines look like sandy outwash. This is something the eye has to get used to, when plotting exploration tactics using a topo map. But a more practical problem is that, although marked as some kind of conservation land, this is actually fenced in cow pasture, and I cannot figure out how to get over to some of the interesting water that is visibly present, looking at the map. You see a stream, you see a swap, it looks perfect! Except that there are no obvious roads through there (I tend to find sites near roads, and only rarely far from them) and, it is not obvious what to use for access. These are my temporary frustrations. So when I drove out there on Saturday (a good 45 minutes from my house) I was disappointed that I had previously driven past here and found fresh barbed wire fencing along the road. This time I was determined to get in. But instead when I parked, I saw woods on the opposite side of the road (see purple outline in the map fragment), stepped into them, and saw a pretty nice pile
I want to make a big deal about the fact that this is wedge-shaped: a single vertical side, with the rest of the pile sloping off indifferently in other directions. 
I called those "ski-jumps" and now want to amend the vocabulary: "wedge-shaped" is more dignified. Regardless of the phrasing, this all is important to me because of where I just recently placed these specific types of piles in the imaginary chronology [click here].
Here is a nice little detail:
There was some lining-up and even spacing going on, not possible to illustrate easily with the ferns in the way:
And there were some pretty big rock piles in there, as previewed the other day:
I don't know if this might be a rock pile with a hollow, or a big platform of some kind. It was not alone. Here is another, which I was trying represent "artistically" through the leaves (little good that does us now):
What the heck was I photo'ing here?:
Probably just trying to give a sense of the general appearance of the site. You could walk right by this without seeing anything. Lucky I started with that easily visible pile. I walked around some more taking pictures. There was a rectangular hole right in there, obviously part of the same collection of structures. 
[By the way I got lucky the next day and found some other wedged shaped piles, with a similar hole which should be considered as part of this "type" of site.]
figured there is probably more to see here. Perhaps I should go back after a few frosts have removed the ferns? 
I think this is the first time I can legitimately include Mt Wachusett in the map fragment. This goes along with my explorations honing in from the south. Well, on the topo map I had noticed this nice brook going up from the road (East Princeton Rd) leading to a little swamp, so I tried to get in there. These areas can be pretty impenetrable with the Mountain Laurel, so I found it easier to head up hill where there was less undergrowth. In the end I decided to finish climbing the little hill - you never know when you might find something up near the top, although most of my finds in this area have been down low near water. But I went up there anyway cuz the walking was easier and was rewarded:
I call this an "aperture" pile because of a deliberate (I guess) hole through the pile:
This is looking out over the beginning of a gully, a few yards below the stone wall that runs across the hill but not quite over the highest point. I climbed up there too, but this seemed to be the location of interest. You would think this vantage point, with a clear shot at Wachusett only a few "feet" away would permit focusing on the mountain. But no, that aperture is pointing west-ish and not towards the mountain. So there is no obvious connection. 
But if you look to the left in the above picture, there is tumbled second rock pile there. Facing back uphill:
I am left with the impression that both piles are contemporary but that the well built aperture pile is a reconstruction. And a recent one at that.
In the foreground is a rock-on-rock with a large rock. In the background, notice the vertical space in the boulder that lines up with the rock-on-rock. We have seen this before. Oh, yeah, at a brook confluence in Sterling, south of Justice Hill Rd where the Orchis grow. Also in northern Westford.
For what it is worth these are also sort of regional:
And a few steps later I start seeing rock piles.
You can see the piles as hints of darker color in the ferns. And you can see the "grid-like" structure. This was a typical site of this type with water to north, and northwest. The site consisted of several clusters of piles. A stone wall separated these from a small peninsula sticking out into a brook, and there were a few larger more broken down piles on the peninsula, like an older site over in there.
I walked around taking pictures of the rock piles and was particularly enamored of this one: 
Let's look at it from above:
See? It is triangular. Some others:
The presence of one larger rock on each of these piles may be significant. I have been finding rock pile sites with triangular rock piles this fall. It is funny how I seem to find the same kinds of rock piles over and over for a while and then I start finding some other kind of site and get into seeing those over and over. What would explain this impression? I do tend to keep exploring in the same places once I find good stuff there. But this is northern Westford, and I just saw the same things in Fitchburg along Falulah Brook, and in Foxboro at the state forest. So I don't get it. Last spring it was all about rock piles with hollows and, frankly I enjoyed them so much this is what I have been hunting for. But now I just keep finding triangular rock piles. Over by a stone wall, a different collection of piles. The layout of the piles, evenly spaced along an arc, is evident enough:
Just to the right in this picture was one pile that was different from all the rest: a broken down platform? 
Or could it be my old friend: a rock piles with hollows? I don't know, it was too far gone. It would have been like a focal point to the arc of the other piles.
These are long gone.
The landowner was right there, so I played dumb and said: "gosh that is a pretty big rock pile". He said: that is what farmers did to clear their field. I said: "they must have had a lot of rock to get rid of". He chuckled and said: we have the glaciers to thank for that. Helpful, he seemed to have all the answers, but I was wondering about mills and dams. Anyway, a few yards down the road I spotted a pile that I would not expect this landowner to explain so easily:
Closer:
Still in Wachusett's shadow. Shall I go back again next weekend?
It was a two part structure. Here is a closer look at one part that was still in good shape. I figured this for some kind of loading bay.
But then, 10 yards away in the woods, what is this for?
The new fall colors are a pleasant change from the universally dark understory green of the summer woods.
It is a little bit of zig-zag stone line, ending in a messy pile under a tree. Other rocks in loose piles around the same low point suggest field clearing. But the zig-zag is carefully made. None of my pictures do much to show this feature.
