Mousa: The Broch of Brochs

Scotland's ancient, unique towers

Mousa is a small island off the coast of mainland Shetland with a Norse name. The 'a' at the end, as in many British place-names, means 'island.' 'Mous' means 'mossy.'

     The 'Mousa boat' ferries you across to the mossy island. It's a nature reserve now, and well worth visiting for the birds and seals alone. But what I wanted to see -- what I'd wanted to see for years -- was already ancient when the Vikings called the island mossy. The Broch of Mousa. It did not disappoint.

The first glimpse of the broch is a striking: a monumental tower, against sky and sea, its walls gently curving like those of a modern cooling tower.

          Amazement only grows from there.

To consider place-names again, the word ‘broch’ is the same as ‘borough’ or ‘bury’. It means ‘fortified place’ or ‘castle.’ Archaeologists adopted the Scottish form ‘broch’ as a name for the towers in the north,’ the dry-stone, ancient towers found all over Scotland but only in Scotland. 

          It’s impossible to accurately date these mysterious towers though it’s broadly agreed that they are ‘Iron Age’ and the oldest may be as much as three thousand years old.  Maeshowe, in Orkney, shows that there was a strong tradition of building dry-stone, corbelled structures, going back five thousand years. (A corbelled roof is where dry-stone slabs are skilfully overlapped to form a smooth, inward curving roof sealed with a single cap-stone.)

Above, the interior of the passage-grave, Maeshowe, on Orkney, showing its  corbelled roof. It is acknowledged as 'the finest Neolithic building surviving in north-west Europe.' The main building is estimated to be at least 5000 years old, making it older than the pyramids. Its entrance is aligned to the setting sun at the midwinter solstice. The last rays of the setting midwinter sun shine down the passage into the ancient grave.

          The immense, upright stone slabs at the corners have no constructive purpose at all. They are not holding up the roof or supporting the walls as you might think. They were already in place before Maeshowe was built. The grave was built around them, as if to preserve or honour them. Possibly they were standing stones. Perhaps the remains of another house or grave. I don't know about you, but this makes my brain boggle.


Mousa’s broch is the most complete of all brochs, still standing 13m (42/43 feet) high. Its twin, the broch of Burraland, which stood on the other side of the strait between Mousa and mainland Shetland, was ‘robbed out’ for building stone and is now only 2-5 metres (8 feet) high. It's sometimes suggested that Mousa's broch was protected from destruction by its position on a small island -- even though Mousa was home to stone-hungry crofters until the 19th century.

          Mousa’s excellent preservation tempts us to take it as a model for all brochs but archaeology shows that Mousa is very untypical. It’s quite small, underwent considerable alteration in antiquity and, overall, is much better built than your average broch. Its superior construction may have been its salvation: it was simply harder to dismantle than other brochs. Whatever preserved it, there’s no doubt it deserves its status as a World Heritage Site.

          To give a simple account of the broch’s interior:



There are no windows in the outer wall and only one entrance, facing the sea. This entrance is 1-5 metres (5 ft) high and the passage behind it is 5 metres (16ft) long. At the end of the passage a ‘bar-hole’ can be seen in the wall. This is where a solid wooden 'bar' would have been put in place, to prevent the door being opened from outside. Whoever lived -- or took shelter -- within these massive walls was keen on some other people staying outside.

          The entrance passage opens into a roughly circular space. At its centre is a hearth and a stone water-tank, reminiscent of the five thousand year old neolithic houses at Orkney’s Skara Brae. 

          Although the outer circumference of Mousa Broch is 15m (45ft), the interior is only 6m (19-20ft) in diameter. Built into the massive base of the broch are three large corbelled cells, differing slightly in size. The largest is about 1-5 metres (5ft) wide, 4 meters (13ft) long and 3 metres (11 ft) high. The doors into these cells are raised above the floor of the broch, perhaps to keep out draughts. Each also has a built-in shelf— again, like Skara Brae, where the bed-spaces had shelves built into the walls beside them.

          Modern houses can have rooms smaller than these without the storage. 

         Above the lintels of the cell-doors, gaps have been deliberately left in the stone-work, possibly to lighten the load each lintel has to bear and to allow light into the cells.

          Mousa's tower is double-skinned, with a ring of outer wall, a ring of inner wall and a gap between them. The outer and inner walls are pinned together with slabs of slate. In this way ‘galleries’ were formed between the walls. It's the way the broch was constructed. The twin walls were built up to a certain height, then slates were used to bridge the gap between them; and then the walls were built higher and 'pinned' again.

          At Mousa it's possible, with some stooping and squeezing, to walk along these galleries to their blind ends. At other brochs, at least where enough of the towers remain to judge, the galleries are too low and too much stone protrudes into them.


Mousa’s builders used the gap between the walls and the pinning slabs to make an interior stair which winds inside the walls right to the top of the tower.


          Beyond this, much is conjecture.


          For instance, the inner wall was constructed with tall rows of gaps, (giving ancient Mousa a startlingly modern ‘architect-designed’ look.) It’s often argued that these gaps were to ‘light the stairwell’ and the corbelled cells, which they certainly do today because now the tower is roofless. But if the tower was roofed in the past, very little natural light would have shone into the broch.


 Roofed or Open?

 There are endless academic arguments about what the summit of the broch was originally like. Today you can climb the stair to the top of the tower and walk about up there, admiring the view. But the tower's top was in ruins until 1960-80, when it was reconstructed. The best educated guesses were used but still -- no one really knows what the broch's summit originally looked like.

          Some argue that there was no walkway or roof. The broch was always open to the weather, as now, allowing the rain and snow to fall down between the concentric walls.

          Another argument insists that the broch was roofed somehow. Maybe the gap between the walls was turfed or thatched, leaving the courtyard open... Maybe the whole top of the broch was covered by a conical thatch, making the broch look like a very tall Iron Age roundhouse.


The Open-to-the-Sky mob reply that the weight of the supporting timbers, plus thatch, pressing outward against the walls would make roofing the broch unlikely. Also, it would make the broch's interior impenetrably dark. (True, but many houses in the past were windowless and dark. Viking longhouses, for instance. Inhabitants spent much of the day outside and, at night, there was fire and lamplight.)

          It's a conundrum. About the roof, I'm neutral but think there must have been some kind of platform up the top there. Why go to the enormous effort of building a dry-stone tower that may, originally, have been more than fifteen metres high (49 ft) , with a stair climbing all the way to the top, if not to stand up there and see further than from ground level?


More Conjecture


At some point in antiquity, a stone wheelhouse was built inside the stone tower. The hearthstone and water tank belong to this wheelhouse, as does the wide stone ‘bench’ that runs around the inside of the tower. (You can see the 'bench' or wall in the photo of the interior above, running around the wall towards the left,)

          The builders of the stone wheelhouse continued to use the broch's corbelled cells, because they left gaps in their own stone wall, to allow them entrance. But they built across the opening to the broch's stairs and galleries, blocking them off. Obviously, they had no love of a sea-view or a need to know who was approaching.

          It was possibly around the time this inner wheelhouse was built that the broch’s entrance was altered, making it much larger. This also meant breaking through the floor of a corbelled cell built above the entrance. (This cell must originally have been entered via the stairs and some kind of upper floor. There are also endless arguments about how this upper floor may have been built into the broch.)


By making Mousa's entrance larger, it was also made less defensive than the entrances of other brochs, such as Dun Carloway on Lewis, where the doorway is much smaller and narrower than Mousa's -- as is the case with almost all other brochs.


          Why were the brochs built?

The theory favoured in the 19th Century was that they were defensive, they were ‘castles.’ Then, in the 'Peace and Love' of the 1960s and 70s, it became fashionable to say that they weren’t defensive because they couldn’t have withstood a determined attack. No, they were merely the prestigious houses of a ruling elite.

          Brochs have tall, thick walls, entirely windowless on the outside. Most brochs have low narrow doors, that make you stoop double to enter. Yet the builders could make corbelled ‘cells’ 3 metres high, so the entrances weren’t low for ease of building. They could construct windows too, so the outer walls were deliberately made without openings.

          Behind the entrance, brochs have long, low, easily defended passages with doors which could be strongly barred. None of this speaks of an elite’s comfort. It positively screams ‘defensive’.

          If a broch couldn’t have withstood a determined attack, neither could the later pele towers of the Borders but no one doubts they were defensive. Rather than withstand ‘determined attack' the peles were meant to discourage attack from largely opportunistic bands of reivers. They said: 'We're ready for you and you won't have it easy, so ride on.'

          The reivers were some three thousand years later but human nature stays much the same. Why invest so much time and effort into building a broch unless there’s somebody around who scares you? People capable of building a broch could have built something equally impressive and much more comfortable.

           Who were the scary people? Unruly neighbours, or passing armies, as with the reivers? The Romans have been suggested— but some brochs were probably built long before any possible appearance of Roman ships off the Scottish coast.

          Again, the truth is, no one knows -- which leads to many more fun arguments.

          Many brochs seem to have had clusters of much smaller wheelhouses around them -- there are faint traces of some at Mousa. This might support the manor-house theory or make the broch a place of refuge during raids. Did they, like the peles, have a signalling beacon on top? Or were they look-out towers, watching for danger approaching from land or sea?

          The majority of brochs are near the sea. Mousa, and the Burraland broch had views up and down the Shetland coast. Dun Carloway stands near a natural harbour on Lewis. During the time they were built, we know there was trade between Ireland and the islands -- and with what was then not yet England.

          A natural harbour often becomes a market-place. Prosperous markets attract thieves and ‘trade’ easily turns into ‘raid’ and slave-taking. If a market town wants to keep its trade, it has to provide protection. Were the brochs garrisons and look-out towers, protecting a market?

          It's quite possible that brochs had several purposes: defensive, if need be, but also providing advance warning of the approach of ships, for good or ill. They discouraged attacks by loudly declaring in stone: ‘We’re ready for you.’ One suggestion is that at least some were 'cathedrals.'

          All of which may be nonsense. Perhaps they were just very expensive and uncomfortable prestige homes for the Iron Age plutocrat. What is without question is that they are astonishing feats of ancient ingenuity and engineering. Anyone who thinks the pre-Roman inhabitants of these islands were 'unsophisticated' should visit the Broch of Mousa.


          And Maeshowe.

          And Skara Brae.


Follow this link for a short video tour of Mousa Broch.

And if you're interested in more discussion about how, or if, the broch was roofed and what exactly it was used for, follow this link