The design of brochs

Unlike the hill-forts found elsewhere in Britain, the brochs of northern Scotland were defensive works designed to protect a relatively small number of people. The term 'broch' is generally used to refer to a free-standing, round, stone-built tower, although several of these may also have been built as a centrepiece of a fortified settlement. Their origins remain something of a mystery. One early theory was that they were built by an influx of newcomers - refugees from the Roman invasion of Britain. However, since no similar structures existed further south, this notion is easy to disprove. Also, most brochs have been dated to between 500 and 200 BC, although they remained in continuous use until the Roman period. The best-surviving broch structure at Mousa in Shetland was built around AD 100, and remained in use for approximately two centuries. The dates apply to other sites too, as at some date after AD 100 the majority of brochs appear to have fallen into disrepair. In structures such as the Broch of Gurness, where the tower was surrounded by a fortified settlement, the village itself seems to have been abandoned, and the stone re-used to construct farm buildings close to the old site.

Fortified Farm

Eildon Hill North, Roxburgh is one of three hills dubbed 'Trimontium' by the Romans, and the site of Scotland's largest hill-fort, enclosing an area of some 16 hectares. It was thought to be the main stronghold of the Selgovae before it was captured by the Romans in AD 80, although recently archaeologists have called this assumption into question. (Historic Scotland)

The communities served by these fortifications must have been small compared to the Iron Age communities who built hill-forts, but then the two types of fortification do not bear close comparison. Given the correlation between hill-fort size and the estimated number of people who lived in or beneath it, only the smallest hill-forts can be compared in scale to these brochs. Both involved a considerable amount of effort for the small agrarian community who built them, particularly when some hill-forts or brochs seem to have been little more than fortified farms, serving at most one or two extended families. It has therefore been suggested that in places like Orkney or Shetland, where these broch structures are common, neighbouring communities pooled their efforts and helped out in the construction of each other's tower - similar to the communal barn-building tradition of the Amish community in the United States.

A typical broch was built using dry-stone walling, and was approximately 20m in diameter. The broch at Mousa stands some 13m high, although others might well have been lower structures - no more than five metres in height. The walls were double-skinned, with a cavity between them wide enough to fit a staircase that wound its way up to the top of the tower. In most large brochs the walls are approximately three metres thick. The structure was entered through a small, low doorway; these were often flanked by guard chambers to improve the security of the fortification. The interior was almost certainly divided into floors, each level being accessed from the stairway and its attendant galleries. In brochs such as Gurness, Midhowe and Mousa the lower floor contained a stone-lined well and food storage pits, which meant the defenders could withstand a lengthy siege. Archaeological evidence suggests that the whole structure was capped by a conical pitched roof of thatch or turf, with timber or even whalebone supports. The same dry-stone walling techniques have been practised in the north of Scotland ever since, as exemplified by old crofts and farm boundary walls.

Brochs always seem to have been built in easily defensible locations, but they would also have had to be constructed close to the arable land worked by

Eildon Hill North, Roxburgh is one of three hills dubbed 'Trimontium' by the Romans, and the site of Scotland's largest hill-fort, enclosing an area of some 16 hectares. It was thought to be the main stronghold of the Selgovae before it was captured by the Romans in AD 80, although recently archaeologists have called this assumption into question. (Historic Scotland)

right Reconstruction of a broch, AD 100

The remains of some 500 brochs are to be found in northern and western Scotland.This illustration shows a reconstruction of a broch based on surviving examples, such as the impressive Broch of Gurness in Orkney.This broch has two thick walls separated by a small passageway. This space serves as a stairwell that winds its way up to the top of the structure, which provides access to the interior floor levels.The broch has a small entrance, protected by guard chambers, while the lower floor of the structure houses a well and storage pits.The broch is approached through a small village, itself protected by a stone wall, as well as a bivallate arrangement of banks and revetted ditches.

The oval perimeter of the hill-fort of St. Catherine's Hill, just outside Winchester, Hampshire.The enclosure (on the right of the picture) slopes gently towards the chalk hill's summit, which is now crowned by a small copse - the site of a medieval chapel. It was constructed around 400 BC, and was occupied until the period of the Roman invasion of Britain. (Courtesy of Marcus Cowper)

the community who built the structure. In many cases the structures were built close to the sea: Gurness and Midhowe were both built on the Orkney seashore, separated from each other by the waters of Eynhallow Sound. The Broch of Gurness is particularly impressive, because a small settlement of at least six sets of houses was built beneath the tower itself. Each was entered from a main passageway that led through the village to the broch. Some of these buildings were entered from small courtyards, flanked by storage sheds. The result resembled a stone-built warren. Surrounding the village was a substantial stone wall at least two metres high, which may have been surmounted by a stone walkway and parapet. The whole complex was entered through a double gate, reached by a stone-lined approach that spanned a ditch running around the landwards side of the village. Beyond this a series of two banks and ditches completed what must have appeared a most formidable site. The neighbouring broch of Midhowe was smaller, with a less developed defensive system surrounding the tower and settlement.

Structures such as these suggested that the society who built them was one under threat, either from neighbouring communities or more likely from outsiders. Were they built as a reaction to a wave of armed Celtic settlers from the south, or were they symbols of community power in an otherwise stable society? So far archaeologists have failed to provide a clear answer. Whoever built them and for whatever reason, they remain as potent reminders of the Iron Age communities who felt the need to defend themselves in such a dramatic fashion.

Age Reason FortificationMidhowe Broch Reconstruction
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