Structure Twenty-Seven

An outstanding example of Neolithic construction

There is no doubt we were spoiled for choice when it came to large, impressive Neolithic buildings. But of them all, it was Structure Twenty-Seven that could truly be said to be jewel in the crown.

Structure Twenty-Seven was a very large sub-rectangular building at the southern end of Trench T.

Built directly on natural boulder clay – the Neolithic ground surface – the structure lay beyond the southern boundary wall and underneath a massive midden mound to the south-east of Trench P.

Excavation of the mound began in 2013, which, at first, was thought to be nothing more than a monumental pile of rubbish – a highly visible symbol of conspicuous consumption in the Neolithic.

In 2014, however, the stump of an upright stone at its bottom suggested there was more to it. The tonnes of deposited ash and domestic refuse were clearly covering something – but what was it? Structural remains began to appear in 2015, and, as work progressed, the sheer scale of the underlying building was revealed.

Although it had been heavily robbed in prehistory, enough survived to show it was an incredible construction. Although there were similarities with elements of Structure Ten, architecturally Twenty-Seven was unlike any other excavated building on site.

2024: Drone orbit of Structure Twenty-Seven at the end of the 2024 fieldwork season. (📷 Scott Pike)

The quality of its spectacular masonry also stood out. While other excavated buildings were generally built using a mix of stone – both quarried locally and re-used – Structure Twenty-Seven was raised using material from a single bed within a single quarry. Stone that was presumably extracted and brought to site specifically for the construction of a remarkable building.

Undoubtedly the finest stonework we’d encountered, the surviving walls were formed by regular courses of perfectly fitted stone, the precision of their placement unsurpassed.

On top of that, the Neolithic builders had also incorporated a deliberate, but very subtle, curve into the length of the side walls.  The outer face was also supported on huge projecting, or stepped, foundation slabs, some over two metres long.

Measuring 17 metres long by 11 metres wide, with walls over two metres thick, access to the rectangular interior was by a single entrance passage in the north end. This was probably defined by upright stone slab, of which only one survived and which was found to be extensively decorated,

The inner chamber measured c11m by 7.5m and had a single, central hearth with stone furniture features lining three of the four walls.

Unfortunately, most of the building’s south-eastern and south-western walls were gone, extensively robbed for stone in antiquity after the building went out of use. But despite its denuded it was abundantly clear that great care and skill had gone into Structure Twenty-Seven’s construction.

This was reinforced in 2022 when the north-western exterior wall was exposed, its quality prompting site director Nick Card to exclaim: “That must surely be the most immaculately constructed and beautiful Neolithic stone wall anywhere!”

And, to be honest, it was.

The north-western wall emerging in 2022/23. (📷 Sigurd Towrie)

2023/24: The surviving outer corners. (📷 Sigurd Towrie)

The north-western wall’s impressive masonry was matched on the south-eastern side, where huge paving slabs extended out from, and in places sat on, the stepped foundations. These also formed the capping stones of a drainage system around Structure Twenty-Seven’s exterior and which connected to a drain exiting the interior under the south-western end wall.

This paving extended around the building, with excavation in 2023 revealing more on its north-western and south-western sides.

The remains of a low wall sat at the outer edge of the paving, perhaps not only defining it but holding back the midden deposits that accrued around the building during its lifetime. Like Structure Ten, Twenty-Seven may have been surrounded by a paved passageway.

In 2023, a sondage – small, deep trench – inserted in the building’s north-eastern corner confirmed that Twenty-Seven’s yellow-clay floor had been laid over a deep, clay platform.

This construction method was akin that previously noted at Maeshowe and Structure Eight at the nearby Barnhouse settlement and confirmed that Structure Twenty-Seven was as well-planned as it was beautifully built.

Stone-clad interior

As we’ve said, Structure Twenty-Seven was a masterpiece in stone, the exquisite masonry of the external walls matched by the care and effort that had gone into its interior.

This space was defined by six enormous slabs, affectionately nicknamed “skirting boards” sunk into the floor against the inner walls.

Measuring up to 4.55m in length and 15cm thick, these side slabs looked for all the world like recumbent standing stones. From the weathering on their upper edges it was clear they were not quarried specifically for Structure Twenty-Seven. Instead, they had been exposed to the elements for some time before being incorporated into the building.

Along each side wall, two of the stone slabs were placed, end-to-end – but not exactly in line to mirror the slight external curve of the walls – with another two along the bottom of each inner end wall.

The prone orthostats protruding from the floor. (📷 Sigurd Towrie)

The scale of these stones became clear in 2024, when a sondage revealed one to be 75cm wide. They were sunk into the floor, held in place by packing stones, to leave only 15cm visible above floor level.

Flat flagstones were inserted into the narrow gap between the “skirting boards” and the inner wall large, cladding Twenty-Seven’s internal wall faces.

The effect must have been stunning, lending the interior the appearance of a stone box – something unlike any other excavated Neolithic building in Orkney to date.

From the centre of the side “rows”, a pair of stone slabs projected inwards, at right angles from the wall, to create two recesses at each side of the chamber.

At each corner were masonry “buttress” features akin to those found in the piered buildings, such as Structures One and Eight. Faced by stone orthostats, these “buttresses” created the same end recesses encountered in some of the other buildings on site.

One of the surviving buttress orthostats – in the north-eastern corner – was found to be decorated with the same rectilinear designs found elsewhere on site. The excavators had noted the slab had unusual, but faint, markings on its surface. Closer examination – and the right light conditions – confirmed there were many incised lines, some forming chevrons and other geometric motifs.

As well as the Neolithic decoration, the stone also had probable “drag marks” relating to its quarrying and transportation.

The remains of the internal ‘skirting boards’ and orthostatic cladding (📷 Sigurd Towrie)

From day one, one of the many questions surrounding Structure Twenty-Seven related to its use of orthostats to divide up its the interior. Most of the excavated buildings on site used one or more pairs of stone piers to define their inner space, so why did the builders of Twenty-Seven decided to use a pair of stone slabs?

Divisional orthostats are found in early Neolithic buildings, most notably the stalled chambered cairns such as Unstan and Midhowe. Their presence in Twenty-Seven was behind the initial idea that the building pre-dated the piered structures in Trench P. But, as we’ll see later, we moved away from that interpretation as more elements of Structure Twenty-Seven were exposed.

Given the careful planning that went into Twenty-Seven’s construction, the use of divisional orthostats was clearly a deliberate choice – just one in a series of specific, and presumably significant, decisions that led to an impressive, yet visually distinct, building.

Abandoning drystone-built piers in favour of a pair of orthostats not only set Twenty-Seven apart from the other buildings but fitted the predominant “theme” of its interior, where no masonry was visible, only orthostats. This was in sharp contrast to the exquisite, coursed masonry on the outside and highlighted the contrast between internal and external appearance and space. 

The decision to use orthostatic dividers may also have harked back to a known, earlier architectural style that perhaps brought with it important notions of ancestry, longevity and status.

Furniture features and the hearth

At the heart of Structure Twenty-Seven was a single, beautifully built, stone hearth.

For years we had pondered whether Twenty-Seven represented some form of funerary building or chambered cairn. The discovery and excavation of the hearth in 2023/2024, however, confirmed that Twenty-Seven was a definitely a construction for the living.

On saying that, the substantial fireplace only contained a shallow deposit of ash overlying a carefully worked and well-fitted stone base. Although the depth of ash could indicate that the building (or at least its fireplace) was not used for a prolonged period of time, it is perhaps more likely that the hearth was thoroughly cleaned out before each use.

Excavation in 2023 also revealed the remains of stone features against the inner faces of the “skirting boards”. Whatever these box-like features represented they had been dismantled in prehistory – presumably when Twenty-Seven was decommissioned – so only traces remained.

Initially we wondered if we had evidence of dismantled furniture, such as the multiple “dressers” in Structure Five, or perhaps bench-like arrangements. The remnants, however, were not as substantial as you’d expect for either of those.

Instead, we might have a situation akin to that within the nearby piered structures, where narrow slabs, embedded into the floor, separated some recesses from the central area and subdivided their internal space.

2023/24: Excavating the furniture features against the prone orthostats. (📷 Sigurd Towrie)

The entrance

When Structure Twenty-Seven began to emerge from its midden cocoon, we were fairly sure its entrance was flanked by a pair of large orthostats – only one of which remained standing. This was confirmed in 2024, when the remnants of the north wall and passageway were exposed. Working around the entrance orthostat it became clear that it also featured very fine, incised decoration.

The motifs were, as usual, geometric, showing triangles and lozenges. However, most of the stone’s surface had flaked off in antiquity so the surviving decoration was not easy to see. A section of the orthostat had also been polished smooth by wear, possibly the result of many people rubbing against it as they entered and left the building.

2024: Close-ups of the incised decoration. (📷 Tom O’Brien)

Like Structure Twelve‘s eastern doorway, a pair of “standing stones” stood directly outside Twenty-Seven’s entrance. Excavation revealed a third orthostat running between these two stones but we think this may have been a later addition – inserted to hold back the growing banks of midden outside.

Timber and a stone roof

Roof tiles among the rubble over the floor deposits, together with the thickness of its walls, suggested Structure Twenty-Seven, like the other buildings on site, had a stone-tiled roof.

In 2023, excavation revealed more tiles littering the surface of the debris layer overlying the Twenty-Seven’s floor. These lay where they fell when the building was deliberately demolished at the end of its life. Among these tiles, however, was a very surprising discovery – Neolithic timber!

The acidic soil conditions at the Ness means that the preservation of organic material is very poor. Where it does survive is usually in small, localised pockets.

Three timber deposits were found on the same day – two in Twenty-Seven and one in Structure Eight. These, however, were nowhere near as substantial as the wooden post fragments found in the floor of Structure Twelve in 2019. What we had were mere mineralised fragments.

By the end of the 2023 season, we had over 50 fragmented timber samples, not to mention a section of a plank measuring about 60cm long.

That the timber had survived is remarkable and further examination will hopefully reveal the type of wood – is it a species known to grow in Neolithic Orkney or recovered driftwood?

The bulk of Structure Twenty-Seven’s wood fragments were found among a deposit of clay – the water content around which undoubtedly provided the anaerobic conditions that contributed to their survival.

We suspect they relate to the demolition of the building’s roof and represent the remains of the wooden A-frames that supported the stone tiles.

Decommissioned, buried and robbed

Following the pattern noted across the site, after going out of use Twenty-Seven was deliberately dismantled and the bulk of its fabric taken away. Its remains were then buried in midden.

Hundreds of animal remains were recovered from the exterior of the north-western corner, including some of the largest cattle bones found on site. The deposit, which also contained sheep and pig bone, had been extensively chopped and was clearly the remains of a major feast or feasts.

This suggests that Twenty-Seven’s demolition was a formal decommissioning event that was accompanied by feasting – perhaps like that encountered outside Structure Ten.

Inside the building, another extensive animal bone deposit was found under one of the huge, toppled orthostats (pictured right).

The conditions under the stone slab had preserved the bone and might indicate that the floor of Twenty-Seven was once covered in feasting debris.

After an unknown period, people returned to the buried remains of Structure Twenty-Seven to collect stone. Digging down through the midden they reached their goal and removed much of the remaining masonry.

This robbing may have been episodic rather than a single event, suggesting it was not necessarily a spur of the moment thing, but perhaps a co-ordinated operation.

The robbers not only knew what they were looking for – high quality and worked stone – but where to find it. They also inserted revetment walls into the surrounding midden to hold it back while they dug for, and retrieved, the prized building material.

As a result, the entire south-eastern wall was removed, along with part of the south-western end and the inner face of the north-western wall. The northern wall was also targeted and one of the “skirting boards” at the north-western side was also removed.

Given the extent of the robbing, there’s little doubt that the recovered stone was for use in another construction. Was Twenty-Seven just a handy source of building material or did its stone have some special significance? Perhaps considered auspicious to incorporate into a new build?

Whatever the case, we don’t know where the robbed stone ended up. Another unexcavated structure on the Ness of Brodgar site? Or a building much further afield?

Early or late?

Although Twenty-Seven was undoubtedly the finest building on site, we don’t have a date for it, so its place in the Ness complex’s long biography is not clear.

Because of the divisional orthostats and the fact it sat on a Neolithic ground surface, under a five-metre-deep midden mound, we originally thought that Structure Twenty-Seven must pre-date most of the other buildings on site. But as more of its remains saw the light of the day, doubts began to grow…

Now, based on architectural similarities, the consensus is that Twenty-Seven is much later in the history of the Ness and probably contemporary with Structure Ten. Built around 2900BC, Ten was the last major construction on site.

Another building in the area that is almost identical to Ten is Structure Eight at the Barnhouse settlement.

It was constructed around 3000BC, when occupation at Barnhouse had ceased, on the site of a large, open-air hearth on the settlement’s periphery – an area that was once a focus of activity, including food consumption and the working of Arran pitchstone.

Although it has not been confirmed by excavation, geophysical survey suggests that Structure Twenty-Seven sat on a similarly peripheral location, beyond the limits of the southern boundary wall.

One of the goals of the 2024 excavation season was to secure organic material that would allow us to radiocarbon date Structure Twenty-Seven’s construction, use and decommissioning.

That was achieved and dating this incredible building is a major aim of our ongoing post-excavation work.

What was Structure Twenty-Seven?

Although elements of Structure Twenty-Seven’s impressive architecture became clearer over the years of excavation, based on the information we currently have the matter of its role remains open to debate.

Like the other excavated buildings on site, it is large, elaborate and would have been a sight to behold. But while we’re confident that the other Ness buildings were gathering places, perhaps relating to specific families or groups, Twenty-Seven stands apart.

Despite the architectural similarities, the building remains distinctly different, not only in its construction but the excavated material recovered (or lack off).

As mentioned above, our interpretations of its function changed over the years but, by the end of fieldwork, there was little doubt that Twenty-Seven was used by people – the “living”.

Was it a variant of the monumental “halls” found over in Trench P. Or something completely different? Perhaps the Orcadian equivalent of an earlier timber building recreated in stone? Or was it a larger version of a structure encountered at Howe, Stromness, in the early 1980s and which was interpreted (questionably) as a “stalled tomb”?

Many questions remain but these will hopefully be answered as we progress our post-excavation analysis of the wealth of data gathered from the Ness complex’s most enigmatic – and beautiful – building.