I told Scott about it, but didn't explain it well, and sort of forgot how I ended up there. So he told me that when I figure out where my "Magic Tower" is - we could visit. Lucky him, we got to go! haha. It's actually kind of cool. It's from the 1700's (though there is a 1903 date carved into the stone (?) renovations, maybe?) and part of the whole Battle @ Bunker Hill era. We took pictures, explored a little, enjoyed the grassy knoll nearby, and were history geeks on a Sunday.
Looks like a sewer cover but it tells the direction of the Old North Church, Bunker Hill, etc.