Structure A is the broch, or Atlantic Roundhouse, at the heart of the site – a massive, sub-circular structure around 21.5m in overall diameter.
The walls of the broch are 5m thick in places, and the structure has an internal diameter of around 11m. It is well-preserved with the remains surviving to over 2m in height at some points. Originally it may have been up to five times that height, or more!
The masonry is extremely high quality, with large, even blocks of sandstone utilised very cleverly to create a very well-finished series of wall faces.
The thick broch walls contain five intramural chambers and the remains of a staircase, indicating that this was a truly monumental complex and multi-storey building.
So far, the investigations of the interior have revealed some very well-preserved internal fixtures as well as a series of floor deposits of laid clay and flagstones and a very healthy volume of artefacts.
Indeed, the layout of the interior conveys one of the most coherent broch floor-plans ever excavated, and this allows us to recover a very detailed and accurate understanding of how the inhabitants moved around and used the space inside the broch.
The discoveries at The Cairns should contribute a great deal to the study of brochs and Iron Age in Scotland.
At present, we are carefully working on the floors and occupation deposits within the broch and these will hopefully offer a picture of the series of activities that occurred inside this remarkable building.
The west “room” seems to have been an area of particularly intense occupation with no less than three separate floors and hearths set up sequentially over time.
Cooking, and food consumption seems to have taken place in the west room, on and around the successive hearths, as evidenced by the volume of burnt and unburnt animal bone, and large volumes of red deer and young pig, and broken pottery vessels.
This species pattern stands out in contrast to other areas of the site, where cattle and sheep/goat predominate and could reflect prestigious dining in the broch. This may indicate the high social status of its inhabitants or that it was the venue for important special events, involving lavish meals.
As well as the animal bone, stone and bone tools, and thousands of pottery sherds recovered, several bronze and iron pins, rings, and glass beads have also come from the broch floors and attest to the jewellery that once adorned the bodies of the broch household.
The end of the broch
Towards the later 2nd or very early 3rd Century AD things inside the broch were changing.
Several of the upright divisions that marked the use of different spaces had slumped or toppled or had been removed, showing that the previously formal layout of the space was giving way. Older hearth settings were no longer in use and were covered over by late floors and deposits.
New hearths were set directly up against the inner wall face of the broch and their damaging impact on the masonry can still be seen, as they scorched, and stained the walls red and black, and cracked the stones.
The final use of the broch overall, seems to have been to process large numbers of small fish, maybe even using the broch as a smokehouse.
Finally, the decision was taken to end the broch altogether.
In preparation for this momentous transformation in the life of the community, a series of interesting deposits were laid out on the uppermost floor of the interior.
These included whole or large parts of animal carcasses, probably the remains of feasting events to mark the occasion. Whole pots were laid on the floor and smashed in situ.
We now know, through the wonders of modern DNA analysis, that a large fin whale, presumably having stranded itself on a nearby beach, was also distributed across the last surface of the broch, as well as its lower infill.
Immediately outside the broch and close to the entrance a truly remarkable deposit was placed tightly against the broch wall.
This involved a large whalebone vessel carved from the same fin whale whose bones were on the broch floor. Into this vessel were placed the remains of three newborn lambs and the mandible of an elderly human.
Propped against the vessel were two right-side red deer antlers and pinning the vessel against the wall was a large saddle quern. This entire deposit would appear to represent an elaborate act of closure.
The infill was undertaken in a series of very methodical and careful ways.
Essentially, the upper reaches of the broch walls were systematically taken down and used to infill the interior space. This was no chaotic rubble tossing operation, however, and the act of infilling the broch with rubble was punctuated by acts of placing caches of artefacts and animal remains, including more of the fin whale carcase.
At the same time the rubble from demolishing the upper reaches of the broch was also used around the eastern end of the broch exterior to cover over the whalebone vessel/human jaw deposit as well as infilling the village building, Structure O.