I hope TMA Eds will forgive me adding a site I may never visit, but from what I have read so far it is a very intriguing place, little known, which may prove to be of considerable importance, and would appear to be in part contemporary with Ness of Brodgar. A tomb of unusual size. See also the separate eponymous entry for the nearby Iron Age part of this complex, and the link within it.
spencer
This lies due north of the of the earlier and unusually large sized chambered tomb for which there is an eponymous but separate site entry. An underpublicised complex of importance. See link below for excavation details, and read the Canmore entry linked to the chambered tomb.