Approaching Via from Brodgar today I noticed just before the Via B&B a large chunk of stone with a reddish cast in parts. Over the way is what used to be a fair size quarry so it might be simply one that got away. Then on my way back I took another look at the dip that it was in, and seeing the rise against Via thought "ha-ha, settlement mound". Looked it up on Canmore and found that in the 19th century a cist (since gone) was found in this barrow. So where that 'boulder' lies is perhaps the scar of excavation.
RCAHMS NMRS record no. HY21NE 2 at HY25841609 is a tumulus that lies between the road and Via, it being 30m N of the house of Via. A 2'x1'x1' cist excavated around 1860 was still visible two decades later. Further excavation in 1879 produced nothing of note that has been related. A large depression in the centre is now filled by rubbish, and at the western end what now looks like a cist merely shows where a wireless aerial used to be. Pre-war another cist, 0.7x0.4m, was found nearby at HY25841610 but had nothing within.