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South Unigarth is a Iron Age souterrain situated on the Orkney Islands, where it represents one of the most distinctive types of underground structure built during the Iron Age in northern Britain. Souterrains—subterranean stone-built chambers and passages—were constructed by communities across Scotland between roughly 800 and 100 BC, serving purposes that likely combined storage, refuge and ritual function. The monument survives as a testament to the engineering capabilities of Iron Age Orkney.
The structure is carved into and built within the local bedrock of Middle Old Red Sandstone, a Devonian-age formation that would have presented both opportunities and challenges to its builders. The varied geology of the underlying stone—comprising conglomerate, sandstone, siltstone and mudstone—offered differing degrees of workability, influencing the construction techniques employed. Such local geological conditions shaped the character and construction method of every Iron Age souterrain.
South Unigarth is protected as a scheduled monument under Historic Environment Scotland reference SM2399, recognising its significance as an archaeological and historical asset. The survival of souterrains on Orkney provides important evidence for understanding Iron Age settlement patterns, technological achievement and social organisation across the northern reaches of the pre-Roman British Isles.
South Unigarth, souterrain is a scheduled monument protected by Historic Environment Scotland under reference SM2399. View the official record →
South Unigarth is a Iron Age souterrain situated on the Orkney Islands, where it represents one of the most distinctive types of underground structure built during the Iron Age in northern Britain. It is designated a Scheduled Ancient Monument by Historic Environment Scotland under reference SM2399.
South Unigarth, souterrain dates from the iron age period, and is classified as a souterrain. It is one of over 32,000 scheduled monuments protected across the UK.
South Unigarth, souterrain is a Scheduled Ancient Monument, legally protected by Historic Environment Scotland — the body responsible for designating and safeguarding heritage sites in Scotland. The official designation reference is SM2399.
Several scheduled monuments lie within 10 km, including Burn of Selta, farmsteads, field system and associated remains (5.3 km), Wasbister, Stenness - Sandwick parish boundary, earthwork (6 km), Ring of Brogar, stone circle, henge and nearby remains (6.4 km).
This page is just one thread. A full Aubrey report pulls together 14 strands of South Unigarth, souterrain's history, each drawn from the record and mapped to the exact spot:
Every location is different. Not every section appears for every place, only what the historical record actually holds turns up in a report.
South Unigarth, souterrain stands on Middle Old Red Sandstone (Undifferentiated), bedrock that formed in the Middle Devonian. The rock here is conglomerate, sandstone, siltstone and mudstone.