A short hop acros the stile from the stones of Stenness, Barnhouse has two anomalous buildings. They certaintly are bigger than both those surrounding them, and the ones at Skara Brae. It has been suggested that they are not dwellings, but maybe some kind of communal space related to the Stones of Stenness.
There are more structures still under the surface, the whole site having not yet been fully excavated.