Structures

The Antonine Wall was much more than just a wall.

The turf rampart was punctuated by forts and fortlets with bath-houses, barracks and high-quality accommodation; a ditch, berm and mound to the north provided additional defences and a road on its southern side connected the Wall with the rest of the Roman Empire. At some forts there are additional defensive features and what may have been signal towers.

Exploration to identify the civilian villages around the forts is still underway, along with investigation of the temporary camps occupied by the labour force during the construction of the Wall.

It was undoubtedly a huge and typically ambitious construction project. But one calculation suggests that, given the available manpower, much of the building of the core linear features could have been completed in about eight months. It is more likely to have been spread over several seasons.

Rampart

The rampart is the core structure of the monument, described by Antoninus Pius’ anonymous biographer as a murus caespiticus: a turf wall. This is a good description as, for most of its length, the rampart was constructed of stacked slabs of turf rather than stone. This was the most common construction method for fort ramparts in Britain during both the 1st century AD and the Antonine period. The easternmost 15km of the Wall, between Bridgeness and Watling Lodge, was constructed of earth or clay, possibly because of a lack of locally available turf.

The rampart was built on top of a stone base ranging in width from about 4.3–4.8m. This base was kerbed, with square-cut stones on the outside and rough uncut stones used as fill. At intervals, culverts across it helped drain away water. The turf rampart was constructed on top of this base, sloping to a height of probably at least 3m. Unsurprisingly, this superstructure of earth or turf has not survived very well and, for most of the length of the Wall, the rampart is no longer visible. Today, however, the best-preserved rampart remains, just west of Rough Castle fort, stand to a height of only about 1.5–1.8m.

It is not known how the top of the rampart was finished. It was probably squared flat on top and may have featured a wooden duckboard walk with a timber palisade along the north edge.

The best place to see the remains of the rampart today is Rough Castle. The best place to see the remains of the stone foundation is New Kilpatrick cemetery.

Berm

The berm is the space between the rampart and ditch. Its width was not consistent throughout, but generally ranged from about 6m to 9m, though it was sometimes narrower and at Croy Hill exceeded 30m. This variability may be the result of miscalculations caused by different teams working on the ditch and rampart, the construction of both features at different times (the ditch being dug before the rampart was constructed, or vice versa), or may have been based on specific decisions to adapt to local landscape features. Recently, a series of pitted obstacles known as cippi have been located at several locations upon the berm.

Ditch

The ditch is a monumental earthwork dug to the north of the rampart and berm. The ditch width ranges from a narrow 4.27m to as wide as 20.73m. In the central sector between Falkirk and Twechar, just west of Bar Hill, the ditch width may have averaged about 12m, with a depth of about 3.6–4m.

The ditch was V-shaped with steep banks cut at an angle of about 30 degrees. In some places, large stones were set on the lips of the ditch, either to mark its line or to prevent material falling back into the ditch. While the ditch is generally continuous along the Wall’s entire length, there are some locations where it appears never to have been dug. This may have been due to the difficulty of digging through hard rock, or the fact that the Wall’s location along craggy outcrops did not require this additional defence. It is difficult to determine the Roman decision-making process, though, as there are also areas (for example, between Croy Hill and Bar Hill) where the ditch was dug despite naturally steep slopes and crags that would have made it unnecessary.

There are lots of places where you can still see the ditch today; some of the most impressive are Watling Lodge, Rough Castle, Seabegs Wood, Croy Hill and Callendar Park.

Outer mound

The outer mound lies immediately to the north of the ditch and was frequently constructed from the materials removed during the digging of the ditch. In some places the outer mound has been so prominent that it appears to have been mistaken by the 18th-century antiquarian Alexander Gordon for the rampart itself; Gordon’s account reveals that he had travelled about two-thirds of the Wall’s length before he was first able to recognise the actual rampart.

Military Way

The military way was the Roman road that stretched the length of the Wall to its south, linking the forts and allowing troops and supplies to move along its length easily. This road linked up with the network of other Roman roads leading north and south across northern Britannia.

This road sat at an average distance of around 40m from the rampart, was 5–5.4m wide, and was cambered to allow for water drainage into drains set to either side.

For several of the Wall forts, this Military Way may also have served as via principalis - the main road through the fort’s interior, crossing the fort from east to west gates. In other cases it featured a series of bypass loops that allowed travel without the need to enter individual forts along the route.

The best place to see the remains of the military way today is Seabegs Wood.

Forts

Seventeen forts were eventually built at regular intervals along the Wall, a dramatic increase from the original plan of just six. Between them they accommodated the 6,000-7,000 men stationed on the Wall. In comparison to other forts throughout Britain and the empire, including those on Hadrian’s Wall to the south, the Antonine Wall forts are, on average, smaller than the norm. All followed the basic Roman design: the classic ‘playing-card’ shape of a rectangle with rounded corners.

The forts themselves were, like the rampart, primarily constructed of turf, with stone or timber internal buildings, and all but one, Bar Hill, were physically attached to the rampart. Within a courtyard surrounded by a protective stone or turf wall, the fort was laid out to a T-shaped interior plan. This was formed by the presence of a major road (the via principalis) running from gate to gate along the long side of the fort, and secondary roads (the via praetoria and via decumana) running to the front and rear gates respectively.

In the centre of the fort was the headquarters building (the principia). Close to it lay the house of the commanding officer and his family (the praetorium), and the granary, large enough to hold a range of food supplies for a year. These buildings were often built of local sandstone if available, and roofed with red tiles. The ordinary soldiers slept in timber barrack blocks, where they cooked their own food, and officers had their own rooms at one end of the block. Even the smallest fort had its own bath-house, with a steam room and sauna, and a communal toilet with space for nine men at a time. Impressive remains survive at Bearsden, where you can see part of the hypocaust, the underfloor heating system.

Attached to the forts, were annexes. These defended enclosures provided additional space for storage, workshops, and stables and often the bath-houses. In a few locations, there is also evidence for a civilian settlement known as the vicus, which grew up organically outside the fort.

The best places to see the remains of forts and bathhouses today are Rough Castle, Bar Hill and Bearsden.

Fortlets

Fortlets were small enclosures attached to the rampart. Very much like forts in their playing-card shape and construction, they were essentially miniature forts measuring about 21m x 18m. Antonine Wall fortlets are similar to the ‘milecastles’ on Hadrian’s Wall, and such small mini-forts are known to have been built across the Empire.

Like the Antonine Wall rampart and the larger forts, the fortlets were constructed of turf on stone bases, and contained timber buildings, probably small barrack-blocks to house the soldiers who were assigned duty there. All known Antonine Wall fortlets had a south and north gate, the latter opening through the rampart and giving access to the area north of the Wall. These northern gateways remain a puzzle, as there are no known causeways across the ditch. It is possible that the gateways were originally used, or intended to be used, for movement north of the Wall, but that something changed and that any such causeways were later removed.

Fortlets may have been located at points roughly mid-way between the larger forts, though they have not yet been identified at every interval. So far, a total of nine fortlets have been definitively identified. The location of some of these in very close proximity, or upon the same location, to full-fledged forts (for example, at Duntocher and Croy Hill) suggests that some forts may have been later additions, perhaps as part of a change in plan. Based on current understandings of the Wall’s building chronology and overall plan, we may expect to find many additional fortlets, probably spaced about one mile apart.

The best place to see the remains of a fortlet today is at Kinneil.

Expansions

Three pairs of small platforms have been found, but no one can be certain what these were for. They appear to be small ‘expansions’ of the rampart, with stone bases and turf superstructure, probably built to the same height as the rampart itself.

They may have been beacon platforms, on which a fire would be lit to communicate a basic signal quickly along the Wall. Another theory is that they were platforms from which catapults or other artillery could be fired.

Lilia and Cippi

At Rough Castle you can see a unique feature of the Wall: a type of man-trap known as lilia. These large oval pits to the north of the ditch and the outer mound may have been the first line of defence for threats coming from the north. Julius Caesar’s men referred to pits like this as lilia or lilies, because of their shape.

Recently another type of smaller pitted obstacle has been identified on the berm at several locations on the Wall. These are known as cippi and have been found on Hadrian’s Wall as well.

Temporary Camps

In addition to the components of the frontier itself, the sites of around twenty temporary camps have been identified through aerial archaeology and photography. None are actually visible on the ground today.

These probably accommodated the labourers while they were constructing the Wall. A rampart surrounded a space where leather tents would have been erected. These temporary camps represent just less than ten per cent of at least 220 Roman camps identified throughout Scotland.

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The Antonine Wall was much more than just a wall.