During the centuries before and after the birth of Christ, the world of northern Europe was going through uncertain and often dangerous times. The civilizations of the
Mediterranean world were making their presence felt. Greek traders gradually opened up the region, selling wine and manufactured goods to the natives. The Romans soon followed, adding tribe after tribe and country after country to their empire until they eventually arrived on the shores of Britain. Needless to say, these events brought utter chaos to the Celtic world and this turmoil is reflected in the construction of fortifications. In the north of Scotland and the islands off its coast these took the form of stone-built towers known as brochs.
Mousa: View of Broch in the Shetland Islands
Brochs are generally tall, conical structures, up 15 metres or so high and about the same across at the base. The outer wall is typically made of two concentric 'skins' bonded together by stone lintels. The space between them is generally occupied by a winding staircase and a number of small cells. They have a single entrance which was heavily defended. The door was recessed, about halfway down the long entrance passage, and there were often guard rooms on either side. About 500 examples have been recorded, mainly in the Northern and Western Isles and on the mainland of
Caithness and Sutherland. Although there are earlier prototypes, the majority seem to date to the period between 100 BC and the arrival of the Romans in the second century AD. They are remarkably uniform in design and some believe that they are the work of a few itinerant 'broch architects'.

Gurness: Plan of the Site
Broadly speaking, there are two regional styles of broch construction common to the
Northern and Western Isles. In the Orkneys and Shetlands, they tend to have solid bases at ground level and are normally surrounded by outbuildings. In the Hebrides, on the other hand, brochs often have ground level galleries and are invariably solitary structures. Which (if either) was the ancestral form is a matter of much inconsequential debate. In addition to cells within the thickness of the walls, the interiors were provided with hearths and were often subdivided into a number of different rooms and compartments. This would seem to indicate that they served as permanent residences rather than simply as refuges in event of an attack.

Gurness: Entrance to the Broch
Mousa in the Shetlands is the best-preserved example of a broch, surviving to a height of 13 metres (of perhaps an original 15 metres). It is 15¼ metres across—but the most of that is taken up by the thick walls which account for 64% the diameter. There is a shallow ledge, or 'scarcement', about two metres above the ground which was most likely designed to carry a timber gallery, supported by posts. Another scarcement two metres higher may well have held the gable ends of a conical roof. A staircase winds clockwise within the wall, up to the summit where a watch could be kept. According to one Norse saga, it was the refugee of a pair of runaway lovers who held their pursuers at bay here in the 12th century.
Bu Broch on Mainland Orkney only survives to a height of about 1½ metres and was excavated in a rescue operation in 1978. Overall, it is nearly twenty metres in diameter, with walls over five metres thick (of which over a quarter was an outer cladding). Unlike many other Orcadian brochs, it had neither outbuildings nor outer rampart and the doorway was a simple opening with no guardroom cells. The interior was about nine metres across and consisted of a central space, with compartments radiating out around it. In the middle, accessible from the entrance, was a well-built semi-circular hearth with a stone kerb and built-in water tank. A number of kitchen implements were recovered along with a lot of burnt pebbles that had been used as potboilers. To the right of the entrance was access to a series of paved compartments, separated by low upright slabs—the last had a door leading into the central space. To the left of the entrance were sockets for radial partitions, suggesting three storage compartments.

Howe, Orkney: Interior of Broch
Howe is also on Mainland Orkney and is very similar to Bu in its setting, construction and layout. Here too, the original walls were buttressed by an outer cladding—after the collapse of an earlier version. The layout of the interior was much the same, with a central space and surrounding compartments—but here a vertical shaft led to a
'souterrain' (a type of underground storage room). Excavations around the exterior revealed the presence of a number of contemporary buildings. Beyond the outbuildings was at least one stone rampart with a single gate opposite the broch entrance.
Gurness: View of Broch from the South
Gurness is the site of another broch-village on the Orkney Mainland, one of a number found along the shores on either side of Eynhallow Sound. Excavations took place in the 1930's but were unpublished until John Hedges produced a summary based on the original plans and notes. The northern part of the site has suffered from coastal erosion, but it would seem that it was protected on the entire landward side by a ditch
4 metres wide and 2 metres deep, faced with drystone walling on its sides, along with a pair of ramparts. The entrance to the site is on the east side and a path runs through the surrounding houses to the entrance to the broch itself.

Gurness: View of the Broch from the Southeast
The broch itself only survives to a height of only about 3½ metres—much of the stone has been robbed. The entrance passage is about 4 metres long, the thickness of the wall, with a massive stone lintel. The door set about halfway along, marked by a sill, checks and bar-holes. Just inside the door, on either side of the passage, is a pair of guard chambers which are linked to a ground level corridor within the thickness of the wall. The interior of the broch, a space about 10 metres in diameter, has been greatly altered by later structures but originally there was the usual kerbed hearth along with a well 4 metres deep and a number of radial compartments. The outer village was built after the broch and the outer wall (but how long after is unknown). Each of the semidetached houses has a kerbed hearth in the main living area and there are a number of cupboards—there was at least one lavatory with a stone seat. The cultural remains include some 850 artefacts, mainly of bone and stone, and a huge amount of pottery.
There is evidence of metalworking but few objects have survived. Mould fragments show that bronze pins and knobbed spear-butts (similar to examples found in Ireland) were manufactured here.

Midhowe: View of Broch from the East
Midhowe is on the opposite side of Eynhallow Sound from Gurness, on the island of
Rousay. It is the only excavated example of a group of three which line the rocky shore. It is flanked by two narrow inlets which are linked by a massive stone rampart which is thickest at the east end, where the entrance passage is located. The outwork seems to have been designed more for display than defence—it is curiously open at the southern end, leaving an unprotected ledge about five metres wide. There is even a set of rock-cut steps leading from the interior of the fort to the ledge. The space between the broch and the outer wall is very narrow, nevertheless it was crowded with stone huts.

Midhowe: View from the North
The entrance to the broch is on the seaward side—an odd choice given the gales that batter the coast. The structure was apparently unstable—it needed to be braced with hundreds of thin slabs wedged into the bedrock around the base. The broch itself is about 18 metres in diameter and survives to a height of just over 4¼ metres. There are fittings for a door and a pair of lateral guard chambers—one of which leads to a ground level gallery. The interior is well-preserved—although the original floor has not been reached. It is divided by thin partitions into two halves (East and West), each of which had a kerbed hearth and was sub-divided into a number of compartments.
Tanks were let into the floor—one of which had been fitted with a lid and was fed by spring of fresh water. Occupation debris included a number of bone pins, combs and handles along with loom-weights, spindle whorls and food-processing equipment— both saddle and rotary querns. Crucible fragments and moulds indicate that bronzeworking went on, although the extent is unclear.
Soon after the Romans arrive on the scene, at the beginning of the second century, the brochs were abandoned. They were impossible to defend against soldiers so welldrilled in engineering and the techniques of siege warfare.