Since it is Fall equinox today, I am posting a site in northern RI that appears to have an equinox alignment. Last year Larry Harrop told me that a tribal member had told him that there is a sacred site in these woods. This is one possibility.
Near the top of a hill is a 300 foot long wall. There are no other walls nearby that may have been joined to it once.
Here is the area plotted in topo software:
I have read of grooved stones with gutters described as "sacrificial stones", especially one at America's Stonehenge in NH. There's no evidence that these stones were used for Aztec-style sacrifices. It is more likely that this boulder was used for some domestic purpose, such as food production, since the grooves are ground smooth. It may have been easier to collect ground corn, acorns, or even paint powder by pushing it along a groove instead of scooping it out of a round mortar.
One thing that always impresses me when viewing plotted waypoints of walls and boulders is the number of astronomical alignments. Some may be pure coincidence, some may be real observation points, and some may reflect a native desire to organize the landscape in respect to the changes of the seasons.
Maybe this wall and boulder were the sacred site, or maybe this other boulder is it:
In any case, the aligned wall and boulder were interesting subject matter for this painting. The best composition was facing away from the sunset.