Roadside attractions - Fitchburg/Ashby

One the way back and forth, having not gotten quite as much physical exercise as I wanted, I watched out the car window for places to explore, and spotted rock piles in a couple of places. This, along with a few other things, was on Old Northfield Rd west of Rt 31, north side of the road:
At a a different place I saw a little domed pile next to the road, explored a bit and found ~8 oval ground piles with quartz. Here was the view from the road:And the nicest pile there:There was also this striking pile - about 10 feet long with a fine piece of quartz at one end:Detail of the quartz:
I was close to the road and only a few feet from someone's backyard, so I was worried about being accosted and hurried in and back out of the woods. So I parked somewhere less conspicuous and snuck back through the woods. Saw this item about which I was curious:Note the six-pack of old Budweiser cans and that the cans are un-opened. I wonder if this might be a donation? since otherwise you need a scenario of someone choosing a rock pile as a place to stash some beer, who then forgot about it.