The Throne - an experiment in Groton

I have been exploring Groton recently because it is not such a long drive, even though it is a town that "usually disappoints" my hunt for stone structures. I joke that the only part of Groton that is interesting is the part that is in Ayer, or Dunstable, or -in this case- Townsend. 

I have a theory that there are certain types of rock pile sites to be found at the headwaters of brooks feeding our important rivers. With the Nashua River sweeping through there on the topo map, my eye was drawn naturally to Robinson Brook and Bancroft Brook that feed into the Nashua from the northwest and originate just north and east of a feature in Groton named "The Throne" on the topo map.

I explored around there years ago but not with the intention of examining the slope leading downhill, from the "Throne" towards those brooks. So I went out there, parked at the northwest edge of the slope (left end of the "old turnpike") and walked east for 3/4 miles, went uphill a couple hundred yards, then turned and walked back west across the slope for 3/4 miles, and then out. It was boring and tiring - an open woods with rocks here and there but nothing interesting. 
I plug along anyway and eventually come to a slight disturbance which I ignore except there is a second nearby. Neither is interesting.

They are next to a slight wet spot and...THERE...something else along the edge of the same wet spot, perhaps some remnants of structure:

Here we look back with the wet spot to the left and the piles along the right hand side.

Charming but uninspiring. They are exactly where they are supposed to be. So I scout around carefully and then continue west. 

Apparently I am now at the "right" height above the waterways. I have a "woah!" moment [here] and find a nice small rectangular mound with a hollow:

How perfectly it sits, looking back down the valley:

And then over a little rise and a lovely further part to this site. Look at the placement of the three boulders [use right-click 'open in new tab' if you want to see it more clearly):

Closeups:

Another view down a little valley, another hollow:

I continued. The theory worked.