This is an intriuging little site on the outskirts of Pitlochry village. Not mentioned by JC , it can be found on an OS map.
It appears to be a classic four poster, which has been ‘improved’ by the addition of some smaller stones (to a total of about 7) in order to complete the arc.
It can be found on the A924 heading north out of Pitlochry in the garden of Faskally Cottages. I wasn’t able to gain access to the garden as no-one was at home and time was limited. The circle can be seen through the trees from the road.