Ring of Brodgar
The stones are set in a circular ditch up to  deep,  wide and  in circumference that was carved out of the solid sandstone bedrock by the ancient residents. Technically, this ditch does not constitute a true henge as there is no sign of an encircling bank of earth and rock. However, many archaeologists refer to this structure as a henge. Aubrey Burl classifies the ditch as a Class II henge; one that has two opposing entrances, in this case on the north-west and south-east.