The chamber under the mound: Rennibister’s Iron Age dead

Wednesday, October 21, 2026 (2:59 PM)

“But after most of what was assumed to be ‘top’ earth had been removed, human skulls and bones were found in large quantities.”

Underground Galleried Building at Rennibister, Orkney. (1927)

Inside the Rennibister earth-house, looking back towards the entrance passage. (📷 Crown Copyright: HES)

By Sigurd Towrie

Located in the yard of a working farm on the south‑eastern shore of the Bay of Firth, the Rennibister earth-house is undoubtedly the most picturesque of the two Orcadian earth‑houses accessible to the public.

It sits in a landscape rich in archaeology — including the Crossiecrown, Wideford, Stonehall and Smerquoy Neolithic settlement sites – as well as the chambered cairns at Quanterness, Wideford Hill and Cuween Hill. This long‑lived prehistoric landscape provides important context for Rennibister’s later Iron Age activity.

Hidden beneath an extensive mound, the subterranean structure was revealed in November 1926 when part of its roof gave way under the weight of a steam-powered threshing machine crossing the farm’s stackyard. Like the earth‑house at Grain, Rennibister is thought to date to the first millennium BC.

Unlike Grain, however, there was no conclusive evidence of above‑ground structures, although the mound itself probably represents the remains of prehistoric settlement, placing the earth‑house within a broader complex rather than as an isolated feature.

Side section drawing of the Rennibister earth-house, Firth. (Marwick. Ancient Monuments in Orkney. 1952) — Side section drawing of the Rennibister earth-house, Firth. (Marwick. *Ancient Monuments in Orkney*. 1952)

Originally, access was through a low entrance passage roughly 3.5 metres long, terminating in a drop of about 0.7 metres into the main chamber. There is no evidence for steps or paving within the passage, suggesting that visitors may have descended through an opening before moving underground.

At only around 70 centimetres high and wide, the entrance would never have been particularly easy to negotiate. Today, access is by way of a modern hatch in the roof, allowing visitors to enter directly into the chamber.

Plan of the Rennibister earth-house. (Marwick. Ancient Monuments in Orkney. 1952) — Plan of the Rennibister earth-house. (Marwick. *Ancient Monuments in Orkney*. 1952)

The chamber measures approximately 3.3 by 2.5 metres and is built of drystone masonry. Its walls rise in a gentle curve to a corbelled roof standing about 1.5 metres at its highest point. As at Grain, four substantial stone pillars support the roof, but Rennibister is distinguished by the presence of five small alcoves recessed into the chamber walls.

“The ambry-like recesses at the wall-angles are of different sizes and at somewhat different levels. The smallest is about 16 inches in height by 13 inches in width, while the largest is 30 inches high by 18 inches wide. These run in from one to two feet or thereby, and at the back no building appears, but simply the natural clay face. One of these recesses is divided into two by a stone shelf half-way up.”

The three‑day 1926 “excavation” showed that the entrance passage was filled with a deposit of earth containing large quantities of shell. Although the chamber itself was largely free of this material, what it did contain was far more striking. Scattered across the floor, under standing water, were the disarticulated remains of 18 individuals: six adults and 12 children. [1]

“The domestic nature of these sites seems to be attested by the nature of the finds from them (excluding Rennibister which must be given special consideration).”

Sandra Ovrevik. The Second Millennium BC and After: The Prehistory of Orkney. (1985)

The “human skulls and bones were found in large quantities”, four of the former placed around the base of the south‑eastern pillar. Fragments of another lay in the recess directly opposite the entrance passage. Another lay between the south‑western pillar and the entrance and the remainder between the south‑eastern and south‑western pillars.

“The greater part of the other bones were found lying on the other side of the chamber” between the north‑western and north‑eastern pillars, although “casual bones were found here and there elsewhere.” [1]

“The disposition of these remains showed perfectly clearly that rearrangement of the bones had taken place at some time subsequent to the decomposition of the bodies.”

The circumstances of the skeletal remains’ deposition remain unclear and continue to intrigue archaeologists almost a century after their discovery.

Analysis suggested the human bodies had not been interred as complete corpses. Examined by Professor Thomas H. Bryce in 1926/27, he concluded:

“The mixture of the bones, if this was the condition in which they were found, does not suggest a burial vault—although, of course, ossuaries are known.” [1]

The bones were disarticulated, indicating that decomposition had occurred elsewhere before the remains were placed within the chamber. From radiocarbon evidence, it appears this deposition took place several centuries after the earth‑house was constructed, implying that Rennibister was not built with a funerary purpose in mind. Instead, the structure appears to have been repurposed for the deposition of human remains later in its life, perhaps after its original function had altered or ceased.

Only one artefact was recovered during the 1926 excavation — an ox scapula, interpreted as a simple digging tool.

“Rennibister has no direct association with a tomb, but the form and contents of the site reflects a close familiarity with the architecture and uses of chambered cairns. Alongside the pattern of re-use seen at Rowiegar and at Quanterness, which stands just round the hill to the east, the form and use of the earth house was a different expression of respect – a kind of emulation.”

Mark Edmonds. Orcadia. (2019)

For many years, Rennibister was regarded as unique among Orcadian earth‑houses because of its association with human remains. Recent discoveries have complicated this picture. Excavations at Windwick, in South Ronaldsay, recovered significant quantities of cremated human bone from an earth‑house, demonstrating that Rennibister is not an isolated case.

The Windwick excavation, led by Martin Carruthers of the UHI Archaeology Institute, encouraged a re‑evaluation of the Rennibister assemblage. Rather than representing a random or accidental accumulation of bones, they may reflect deliberate and meaningful acts of deposition linked to remembrance, ancestry and the treatment of the dead.

In this broader context, Rennibister is no longer an anomalous curiosity but part of growing evidence that some Orcadian earth‑houses played a role in the ritual and mortuary practices of Iron Age communities.

Notes

[1] Marwick, H. (1927) Underground Galleried Building at Rennibister, Orkney. Proceedings of the Society of Antiquaries of Scotland, 61, 296-301. https://doi.org/10.9750/PSAS.061.296.301