The last pile at Blood Hill. About "hollows" in rock piles.

This is a most beautiful example of a rectangular mound with a hollow and a "tail" - a variation that involves a deep inner hole and a broad pavement, to one side, for a "tail". This pile was all by itself on the smooth northeastern slope of the hill, more or less directly north of the main valley I described earlier.

Lots of additional structure visible. First picture, a sort of "vestibule" faces the viewer. Second picture at the right rear, there is another little auxiliary divet. 
Let me repeat myself about piles with hollows. There are three hypotheses that have been voiced:
1: The hollow is from vandalism - people removing rocks from the pile.
2. The hollow is added to the pile later, or built in from the beginning. It is a place for a person to sit, as in a "vision quest pit" or "thunderbird nest".
3. The hollow is a built in architectural feature to hold something (a body or an offering) that is now gone. The hollow might have been open to the air, or the result of collapse of an inner chamber.

I have looked at hundreds of sites and many hundreds of examples and I can tell you: hypotheses #1 and #2 do not fit all the evidence.

Evidence against vandalism
- The hollows are usually symmetrically placed. Sometimes there are two adjacent hollows. 
- There are no scattered rocks around the edges of the pile, that could have been removed from the hole.
- A broad spectrum of variations in pile height from 6 foot tall walls to 1 inch of rock poking up through the dead leaves. All have the hollow. In other words, the hollow is there even when there is almost no rock pile to be seen. You have seen rectangular outlines on the ground. There is no evidence of vandalism and not much evidence for a pile. Like the Cheshire Cat: can there be vandalism without a rock pile?
 - It is inconceivable that the same shapes appear in piles from Nova Scotia to Georgia. Are we believing that "hardy Yankee" vandals did the exact same thing..coast to coast...at sites scattered from 'nearby' to 'vary inaccessible'? Consistency is evidence of design not of destructiveness. We give a "no" to Bakunin: the destructive act is NOT the creative act.
- A well built hole: sometimes the hollow is a vertical sided hole that is carefully made. It could not have resulted from vandalism.

Evidence against "Vision Quest Pits"
- A lack of any positive evidence: no one ever was observed using a rock pile as a "seat". There are no recorded instances. Several people include it in their speculations, notably an old indian who spoke (in a YouTube I watched) about the hollowed piles being made by "old ones...who went before". 
- It is inconsistent with actual variations in pile shape. There is a continuum of shapes from simple outlines to deep holes in large piles. Sometimes the hollow is too deep to see out of (which would pretty much be the case in the pile pictured above).
- Wrong sized hole: frequently enough the hole is 15 inches across. I joke that these are "cup holders". They could not perform any function involving a seated person.

In "Science" you take your hypotheses and test them...and test them again. I eliminated the "vandalism" hypothesis after seeing many examples with the same clean design and no scattered rocks. I eliminated the "Vision Quest Pit" hypothesis when observing small hollows, overly deep holes and the continuous spectrum of shapes only some of which could function as a place to sit.