Small things at Wilder Brook

On the hill to the west of the lower blue dot (here) a couple of subtle things:

If you look closely, there are 4 rocks visible on the surface, in a slight curve. Statistically impossible, this must be the work of man. Another view from off to the side, where there was a white rock.

Near there, a low place. Is that another?

No, it is part of a larger structure:

The Wilder Brook area is full of things to look at. One notes it is a portage place between the CT and Merrimack river systems.