Unst is nearer to Bergen in Norway than it is to Edinburgh, and it was Norwegian before it was Scottish, the result of Viking invasions in the 8th century. Before that, it was inhabited by the Picts.
Nobody is really sure what happened, of course (unlike the transfer from Norwegian to Scottish power in the 14th century, the political shenanigans of which are well documented – needless to say, Norway might have a valid claim to Shetland, even today…).
All these circles were easily accessible: more alive than Stonehenge, say, and far less crowded than Avebury.
(I recently came across negatives from Callanish, my all-time favourite group of circles and a magical place; sometime I shall scan them, and post them here.)