Looks like the reminant of a neolithic tomb to me?the cup and ring type spirals are a give away.perhaps it is parts of various monuments brought together? I visited it years ago but will go back and examine the giants grave in two days time as I'll be staying over in Penrith enroute to Keswick. The artwork looks very like that found on the little Meg stones.
Something is not right. This message is just to keep things from messing up down the road