The Carn Meini stone river

Here is the Carn Meini stone stream or stone river, towards the left edge of the photo, and to the right of the winding stream cutting.  You can see that it runs downslope from one of the rocky outcrops at the western end of Carn Meini, within a broad depression.  There is no way that this could be a man-made feature.

Above is a splendid photo from Skinnyde -- taken somewhere on the Falklands.  The "stone river" near Carn Meini is very similar indeed, although archaeologists have speculated that it might be an ancient roadway or route used for the transport of bluestones downslope from the mythical bluestone quarry up among the rock outcrops.  

Here is a description of how stone runs are formed.

From Wikipedia:  A stone run is a conspicuous rock landform, a result of the erosion of particular rock varieties caused by myriad freezing-thawing cycles taking place in periglacial conditions during the last Ice Age.
The actual formation of stone runs involved no less than five processes: weathering, solifluction, frost heaving, frost sorting, and washing.  The stone runs are essentially different from moraines, rock glaciers, and rock flows or other rock phenomena involving the actual flow of rock blocks under stress that is sufficient to break down the cement or to cause crushing of the angularities and points of the boulders.