A geophysics image produced for an investigation at Redland in the parish of Firth of a site occupied ~3300-2000BCE clearly shows a boundary around round houses, and this wall/ditch has been compared by those concerned with the Great Wall at the Ness of Brodgar in the parish of Stenness.
orkneyarchaeologysociety.org.uk/index.php/features/redlands-investigtion
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This dig appears on Orkneyjar as Muckquoy, for which place I have previously summarised finds in a weblog themodernantiquarian.com/post/113140/.html