Moon Hill Revisited

Recently I visited Moon Hill to find more markers suggesting astronomical alignments.  While I didn't find any more  alignments, I did find more evidence the site has been used in the distant and recent past.
Here is a young bent tree pointing the way.

There were several cairns I never noticed before, including this one with a brick on top.

Here is the other side of the propped boulders on top of the hill.  That rotted tree was not there previously.

Donation or prank? There was also a rusty bucket nearby.  Finally, near the old building foundation I noticed this rock with a round cavity about 8 inches across.

A grinding stone from pre-contact times?  This suggests hundreds, if not thousands, of years of history in less than one acre.