"Perhaps the space within the circle was seen more as the primeval sanctuary"...
Lateral thinking - the primeval was outside the circle, the circle is the beginning of civilisation - thought everyone knew that ;) in it this circle, which is the ego of course, religion, politics are formed, manipulation and domination takes place and the whole history of humanity evolves..... and since stone circles sometimes replace timber circles (which I suppose could be construed as primeval forest!) they are not a "natural" sanctuary... just a more durable material.