Revisiting a site in Boxborough

What I recommended re-reading here mentions a site in Boxborough near Wolf Swamp with a central mound and another site in Leominster where a curve of 3 rock-on-rock structures led up to a central mound. I went back to visit the Boxborough site and was reminded that there are actually 2 mounds with hollows and they are "joined" by a curve of 3 rock-on-rocks. So these sites had one or more mound with a hollow, curves of small structures connected to them, and outlying marker piles. Some of these mounds have one nice chunk of quartz somewhere on their outer surface.