Most people familiar with Papago Park's Hole in the Rock think instantly of this view as you approach from behind the rock.
I went up around noon on the 21st to see if there was any equinox shadows or somthing that might indicate early inhabitants used this area as a marker.
As one approaches from the rear, the other hole in the rock is visible. The upper hole. As I walked up I noticed the moon was at a level where it could be seen through the upper hole.
Here is a closer view
Granted this photo was right about noon - maybe 5 after and kind of shows the point of the hole on a pointed rock sticking up.
So it MAY be an indicator, but the true half-way point of the sun is not at noon on this day. Much closer to 1 or 1:30, but I couldn't be there then.
An interesting possibility is the line of the rock shadow closing in on the change in rock at the base. Will have to see if I can get out there another time and see what happens.