Illuminating Isurium

37 mins read

Exploring Aldborough’s Roman remains

Extensive geophysical investigations over the last ten years have illuminated the long-buried remains of Isurium Brigantum, once the capital of the Romanised Brigantes. Here, Rose Ferraby is carrying out magnetometry survey as part of the Aldborough Roman Town Project. CREDIT: Tom Ferraby

Isurium Brigantum was a thriving and prosperous Roman town in what is now North Yorkshire, but it has attracted relatively little modern archaeological attention. Now, though, a decade of geophysical surveys have shed vivid light on its make-up, and a wide-ranging new book presents a compelling narrative for how the once-bustling settlement evolved. Carly Hilts reports.

Almost 2,000 years ago, a thriving Roman settlement was founded deep within the territory of the Iron Age Brigantes, in what today is North Yorkshire. Located c.25km north-west of the legionary fortress at Eboracum (York), and lying on a key route to the Roman frontier at Hadrian’s Wall, Isurium Brigantum was the most northerly administrative centre in eastern Britannia. Unlike many of its contemporaries, though, this once-thriving settlement did not develop into a modern town. Instead, the site is today home to the village of Aldborough, and its Roman predecessor now lies partly beneath its houses, and partly beneath open farmland. While this might seem a humble legacy for a once-important urban centre, though, it represents a fantastic archaeological opportunity – and since 2009 Professor Martin Millett and Dr Rose Ferraby of the University of Cambridge have been carrying out extensive geophysical surveys of much of the town and its suburbs, bringing its long-buried streets to light once more (see CA 312).

Millett and Ferraby have now published Isurium Brigantum: an archaeological survey of Roman Aldborough (see ‘Further information’ below), drawing together the results of centuries of previous excavations and their more-recent Aldborough Roman Town Project to present the latest thinking on Isurium. This synthesis combines an impressive overview of past research on the site and a detailed proposed chronology for how the settlement evolved. Interestingly (and unusually, Millett and Ferraby note), much of what we know about Isurium Brigantum was established before the advent of modern archaeology. The site’s Roman connections were first rediscovered in the 16th century, and its remains attracted antiquarian interest across the 17th to 19th centuries – interest that only grew when these early explorations uncovered a series of elaborate mosaics.

This map shows Aldborough (Roman Isurium Brigantum) in relation to known Roman roads in the region. Roecliffe fort lies a short distance to the west. CREDIT: Rose Ferraby, using data from Digital Atlas of the Roman Empire, CC BY-SA 3.0

The first half of the 19th century marked something of a golden age for these investigations, after much of the site was purchased by a wealthy local man, Andrew Lawson, in 1834. A keen antiquarian himself, Lawson actively encouraged exploration of Isurium’s remains, and as he redeveloped Aldborough Manor and its estate, he cleared and planned a number of Roman buildings, incorporating some of them into his garden design and organising a number of favourite finds, including stonework and inscriptions, along a special walk where they could be admired. As a result of this enthusiasm, in 1852 Henry Ecroyd Smith published Reliquae Isurianae, one of the earliest accounts of any town in Roman Britain, in which he mapped most of the discoveries made on the site up to that point; and in 1863 the Museum Isuriarum was opened on the site.

After this flurry of activity, though, investigations at Aldborough largely ended until the 1930s, when the Roman Antiquities Section of the Yorkshire Archaeological Society explored elements of the town’s defences. Small-scale excavations were also undertaken by the Royal Commission on Historical Monuments for England and by the Ministry of Public Buildings & Works in the 1950s and 1970s, with the results only published after a long delay. More recently, research has focused on Isurium’s artefacts, with Yorkshire Archaeological Society carrying out field-walking surveys in the 1980s and 1990s, and English Heritage funding a study of the coins and glass from the site in this latter decade. All of these investigations have produced fascinating snapshots of different aspects of Isurium’s story, but there was no sense of the wider picture, or a clear timeline of how the town had developed. Martin Millett and Rose Ferraby have set out to weave these disparate threads into a more-coherent pattern, to investigate how Isurium’s fortunes waxed and waned centuries ago.

Isurium never developed into a modern town; although the village of Aldborough covers the southern portion of the settlement, much of its northern extent lies beneath open fields. The village church, which can be seen in the centre of this photo, stands over the heart of the Roman forum. CREDIT: Dominic Powlesland

EXPLORING ORIGINS

Many of Roman Britain’s major urban centres – St Albans, Silchester, Canterbury, Chichester – are known to have been founded on the location of significant Iron Age settlements, but Isurium Brigantum seems to have sprung into being from what was essentially virgin soil. It is true that pre-Roman occupation of the immediate area has long been poorly understood, partly because the local soils do not generally produce clear cropmarks, Millett and Ferraby attest, and partly because there have been few major modern developments near the site (which is a Scheduled Ancient Monument) which might uncover traces of prehistoric settlement. However, the authors’ surveys have not found any evidence that the Roman town was the successor of an indigenous power centre. That is not to say that Iron Age activity was absent in the area – pollen analysis testifies to arable farming and woodland clearance during the late Iron Age, while 2018’s particularly hot and dry summer, which revealed the ghostly outlines of buried features across Britain and Ireland (see CA 343), also created cropmarks in the wider Aldborough environs, showing enclosures scattered across the landscape.

When, then, was Isurium founded? Finds from other sites in the region, such as Stanwick and Scotch Corner, attest to long-standing links between the Brigantes and the Roman world, with goods being imported at least as early as the Claudian conquest of AD 43 (see CA 365). The earliest evidence for Roman activity in the immediate area, though, comes from Roecliffe fort (partly excavated during widening of the A1 in 1993-1995), which lies 2km to the west of Aldborough at a crossing point on the Ure. The fort is thought to have been built in c.AD 71-85 (possibly slightly earlier), in the aftermath of a turbulent period when long-running conflict between the Brigantian queen Cartimandua and her estranged husband culminated in Roman annexation of the territory. It appears that Isurium may have been founded at around the same time, and traditionally it has been suggested that the town may have begun life as another fort, possibly operating alongside and ultimately succeeding the garrison at Roecliffe. Millett and Ferraby argue that new understanding of the date, scale, and character of this settlement demands a rethink, however.

Aldborough saw a flurry of antiquarian activity in the early 19th century. Roman remains
were incorporated into the garden design of enthusiastic landowner Andrew Lawson; this 19th-century photograph shows a portion of the town wall and other masonry. CREDIT: reproduced courtesy of Sir Andrew Lawson-Tancred

Pinning down the date of Isurium’s foundation is not a straightforward task, but Richard Brickstock has carried out a comprehensive reassessment both of antiquarian collections from the site and more recent metal-detector discoveries – analysis that places a significant proportion of these finds in the Flavian period (AD 69-96). Given the massive military movement into the north from AD 71, might this strengthen the case for a military origin? Certainly, there are many finds from Isurium with a distinctly martial flavour. The pottery assemblage, in particular, speaks of connections to military supply networks during the earliest phase of the site’s occupation, while a number of tiles stamped with the names of different units have also been recovered. These refer to Legio IX Hispana (who were based at York c.AD 71-122), Legio VI Victrix (who replaced IX Hispana at York after 122), and Cohors III Breucorum, a group from Pannonia in central Europe, which was first attested in Britain in AD 122, possibly arriving in connection with the construction of Hadrian’s Wall.

This postcard shows the museum interior in the mid-20th century. CREDIT: reproduced courtesy of Sir Andrew Lawson-Tancred

This is not the only link between Aldborough and the Roman frontier: the site is named twice in the famous writing tablets discovered at Vindolanda (an auxiliary fort just south of Hadrian’s Wall), in references that suggest Isurium was a well-known stopping point on the military route to the north, together with Vinovia (Binchester), Cataractonium (Catterick), and Bremesio (possibly Piercebridge). Further clues come from the outline of a structure excavated at Aldborough in the 1930s: investigations in the north-east of the Roman town revealed a U-shaped foundation trench, accompanied by what has been interpreted as a pair of parallel eaves, drip gullies, and a beam slot. These traces are reminiscent of a kind of building known from early military sites, Millett and Ferraby report – tantalisingly, such 1st-century sleeper-beam granaries are only found in military contexts in northern Britain, though they are known from civilian sites in the south.

So far, the evidence seems compelling – but, the authors emphasise, military finds need not indicate the presence of a fort. Soldiers could be present for a number of reasons: the Roman army was involved in tasks ranging from surveying and construction to diplomacy and overseeing industry (possibly including lead- and silver-mining in the Pennines during the later 1st century), and military trade networks are known to have dominated the local economy following the army’s influx into the region after AD 71. Millett and Ferraby also emphasise that early Isurium’s design was very different to known Flavian auxiliary forts, with pottery distribution suggesting that its initial occupation was concentrated in a 10ha area of level ground between the edge of the river terrace and the road between York and Roecliffe. This is much more space than would have been required for an auxiliary fort – compare Roecliffe (2.5ha), Hayton (1.5ha, about 30 miles to the south-east near Pocklington), and Elginhaugh (1.6ha, just southeast of Edinburgh).

The earliest evidence of Roman activity in the immediate area is Roecliffe fort, which lies 2km to the west at a crossing-point on the River Ure. CREDIT: Rose Ferraby, Crown copyright and database rights 2018 Ordnance Survey

Instead, the authors suggest that we should imagine a civilian settlement that prospered through provisioning and supporting military campaigns in the area – perhaps similar in operation to Roman London, another thriving centre of trade that also lacked an Iron Age predecessor. Isurium was located on a key intersection between Dere Street and the River Ure – well positioned for facilitating the movement of bulky goods like grain, and also for speeding communications northwards towards the frontier.

ISURIUM EVOLVES

Rose Ferraby and Jess Ogden carrying out ground penetrating radar survey in the area of the Roman forum. CREDIT: Martin Millett

How did the settlement develop? Finds analysis combined with geophysical survey evokes a densely occupied but fairly unstructured settlement within the initial 10ha area, which gradually expanded to the south between c.AD 70 and 120. From these slightly chaotic origins, though, by c.AD 120 something rather more formal had crystalised: previously only hinted at in aerial photos, a dramatic image of a regimented street-grid covering more than 17ha has been laid bare by Millett and Ferraby’s surveys. These carefully planned roads are easiest to see in the northern part of the town, which lies beneath open fields – this includes the main north–south street, as well as a series of smaller streets running parallel in a regular pattern. A determined effort also saw three large terraces cut into the local hillside and the town extending over these new surfaces to overlook their northern neighbours. The principal east–west street is less clear, but appears to follow the route of the early road running between York and the river-crossing near Roecliffe.


Isurium had a carefully planned and strikingly regimented street-grid. The southern part of the town spread over three terraces, which were deliberately cut into the hillside. CREDIT: Rose Ferraby, Crown copyright and database rights 2018 Ordnance Survey

On the southern side of this road lies the distinctive rectangular space of the forum. Set slightly back from the road, perhaps suggesting that it was surrounded by a colonnade, it forms an integral part of the grid layout, and its creation would have been a significant planning exercise, involving cutting into the foot of the hillslope to create the lowest of the three hill terraces. Helpfully, the major levelling-up work involved in its construction has sealed the only solid dating evidence associated with any of Isurium’s public facilities. This includes the footprints of a number of small Flavian-period structures, as well as pottery fragments indicating that the forum was not built before c.AD 120. Another clue comes from an antiquarian find: an aureus of Trajan, dating to AD 112- 114, which was recovered from the stone foundations of the forum in 1770. Valuable gold coins like these would have been carefully looked after, Millett and Ferraby say, arguing that the Isurium example is unlikely to represent a casual loss. Might it instead have been deliberately placed in the foundations as a votive gesture marking the forum’s construction – and, with it, the cementing of the settlement’s civic status?

Interpretation of GPR survey results along the principal east–west street and to the south. The forum can be seen in the centre-right of the image; the town wall and west gate (opening on to the road to Roecliffe) lie to the far left. CREDIT: Rose Ferraby, Crown copyright and database rights 2018 Ordnance Survey

While the dimensions of Isurium’s street-grid suggest it was one of the smallest civitas capitals in the province, its inhabitants nevertheless enjoyed access to all the trappings of Roman-style life. The identification of a number of public buildings adds to a picture of a community with developing status – not least the town’s amphitheatre, which crowned the highest point of the hillside. Its remains can still be seen, with earthworks preserving a section of seating bank, and its arena still present as a hollow in the hilltop, but its purpose had long been debated. Geophysical survey has now confirmed for the first time that it was indeed an amphitheatre, revealing its full plan (60m by 40m) – though its date is harder to pin down. The amphitheatre lies a considerable distance from the initial focus of 1st-century activity, perhaps suggesting that the town had already expanded south by the time of its construction, while evidence for how it was accessed suggests that it pre-dates the town walls (which were probably built in the 2nd century, as we will discuss below).

There may also have been a public bathhouse: fieldwalking has revealed quantities of hypocaust tiles dating to c.AD 100-180, while geophysical survey may have located the structure itself. Although the remains are thickly covered with rubble, a strong signal picked out a range of three large rooms with a trio of smaller spaces behind it; a large rectangular feature close-by might be the outline of an associated palaestra, or exercise yard.

It has long been debated whether the earthworks to the south of Aldborough represent an amphitheatre; geophysical survey has now revealed its entire plan, confirming its function, as can be seen in this gradiometry plot. CREDIT: Rose Ferraby, Crown copyright and database rights 2018 Ordnance Survey

As for the settlement’s religious activities, two possible temples have been located through geophysics. One of these, in the north-west part of the town, is represented by a 17.5m by 11m structure made up of two rooms with an annexe to the west and possible steps to the east. Set in an open courtyard, it has been interpreted as a twin-celled temple. The other example lies on a terrace to the south, overlooking the town. Its outline forms a 15m by 6m rectangle, again with possible steps at one end (this time, facing north). Although neither of these buildings can be dated, the fact that they appear to follow Classical rather than Romano-Celtic design norms suggests that they may be earlier rather than later, Millett and Ferraby write. Other insights come from excavated evidence: the discovery of part of an altar dedicated to ‘Jupiter Best and Greatest and the Mother Goddess’ hints at which deities were particularly venerated by the town’s population, as do pieces of sculpted reliefs depicting Mercury and one of the enigmatic hooded figures known as the Genii Cucullati.

The amphitheatre’s north seating bank still survives as an earthwork.

DWELLINGS AND DEFENCES

Above all, the emerging image is one of a carefully designed, flourishing town – one that, despite its modest size, was evidently prospering. We can see further signs of this in the houses of its inhabitants. Millett and Ferraby’s surveys suggest that the northern part of the town was very densely occupied, packed with strip buildings of various kinds, together with several aisled halls – a bustling, crowded, urban centre. Evidence for the southern portion of the town is patchier, as more of it lies beneath modern Aldborough, but antiquarian excavations can shed some light on its make-up: it appears to have included an impressive cluster of large, well-appointed townhouses adorned with fine mosaic floors. One particularly prominent example fronted on to the town’s main east–west road: it boasted a mosaic corridor more than 10m long, forming the western side of a colonnaded courtyard. Another, located on the principal north–south road, had a long room with a curved apsidal end, which may represent a triclinium or formal dining room. This space was decorated with two mosaics, the larger of which bore an image of the Muses, accompanied by a Greek inscription (for which reason it is known as the ‘Helicon mosaic’).

This intricate mosaic once adorned a corridor more than 10m long, which belonged to a grand townhouse in the south of Isurium.

Most of the mosaics described above have been stylistically dated to the 4th century, though one courtyard house in the southern part of the town had two mosaics that are late-2nd-century in date. It is not clear whether the apparent difference in character between the crowded north and the large houses of the south represents the reality of Isurium’s layout, or whether it simply reflects differences in surviving evidence, though. What does seem clear is that, for much of Isurium’s existence, it counted some undeniably wealthy people among its population.

The town’s status was further solidified by the creation of a wall circuit enclosing a rough rectangle of c.21.6ha. Dating Roman-British town defences is often fraught with difficulty – particularly when, as at Aldborough, the walls have been extensively robbed – but previous investigations have established that Isurium’s walls post-date both the creation of the town’s formal street-grid (as traces of early road surfaces have been identified beneath them) and the amphitheatre – on balance, Millett and Ferraby suggest that they were built in the 2nd century.

Parts of the forum foundations were re-excavated in 2017, as part of the Aldborough Roman Town Project. Unusually, it appears to have been built in stone from the beginning. CREDIT: M N Hessey

Four gates allowed people and goods to pass through the walls at each point of the compass; all of these have had limited archaeological exploration and, though none have been fully planned, they appear to have been substantial constructions. Excavation of the North Gate in 1924 and 1938 revealed evidence for a c.10m carriageway running through it, with a possible central footing hinting at a double portal to allow the passage of traffic in both directions. Why, though, were the walls built? This may seem like a strange question, but it is possible that the motivation was not purely defensive: the walls on the south and east sides of the town are screened by natural features which mean that they are not visible to anyone approaching from this direction – hardly a deterrent to would-be attackers – and travellers on these roads would also not be seen by the town’s inhabitants until they were almost at the gates. Instead, might the walls have been seen as a natural part of the town’s evolution, an undeniable statement of importance and civic pride?

Overlooking the re-excavation of part of a domestic bathhouse associated with a townhouse identified in the southern part of the town. This dwelling also had two 2nd-century mosaics; the structures in the background were constructed in the 1830s and 1840s to protect them after their excavation.

Whatever their original intention, the walls were later significantly enhanced with external towers and new ditches dug further out from the defences. (Dating evidence for these works is sparse, but the bank behind the north wall was built up in c.350- 400, possibly as part of this wider improvement project.) Two annexes were also added to the north-east side of the circuit: might they have been intended as secure storage for goods moving along the road/river route to the frontier, or could they have been connected to a more-formalised system of tax collection that is thought to have emerged at around this time? Further commercial clues also come from a sequence of three large structures that were identified inside the north wall in 1924. Substantially built and measuring c.60m by 28m each, with three long internal rooms, they are thought to be horrea, or warehouses. In 2018, the Aldborough Roman Town Project reinvestigated one of these buildings, recovering pottery that suggests it was constructed c.250-300 – and, while no conclusive evidence was excavated to confirm that these buildings were warehouses, their scale fits with the picture of Isurium as a major provisioning point helping to move large quantities of goods northwards.

SURVEYING THE SUBURBS

These phase maps show a suggested sequence for how Isurium evolved, beginning as an open settlement covering around 10ha, before developing into a more formal street-grid, expanding to the south and acquiring public buildings like an amphitheatre; it later acquired a sturdy wall circuit, which was subsequently reinforced with extra defensive ditches, towers, and annexes. CREDIT: Rose Ferraby, Crown copyright and database rights 2018 Ordnance Survey

Isurium’s activity was not confined solely to the bounds of the town walls: it was surrounded by suburbs hosting diverse industrial and ritual activities. Interestingly, different activities are associated with different areas outside the town: the route to the north seems to have been particularly busy, with evidence of dense occupation outside the North Gate, and the road frontage scattered with numerous buildings surrounded by enclosures. Isurium also followed the Roman custom of interring the dead outside the town walls: organised cemeteries flank the road outside the East Gate (the road to York), with large mausolea surrounded by funerary enclosures. Further from the walls were areas used for cremation burials, while less-formal cemeteries seem to have lain outside the South Gate, in an area otherwise dominated by the amphitheatre.

Outside the East Gate, where the soil contains clay suitable for ceramic manufacture, mortaria and coarse wares were being made in c.100-140, while there is also possible evidence for stone-quarrying and kilns. These busy suburbs add to our understanding of Isurium as a successful town, flourishing for around 150 years. Analysis of finds from the 1980s-1990s fieldwalking surveys reveals a peak of activity outside the walls in the later 2nd century, with another peak in the mid-4th century, gradually tailing off thereafter. This decline coincides with when the town walls are thought to have been reinforced: might this indicate extramural occupation moving back inside the town for some reason that, for now, remains obscure?

Geophysical survey outside the town walls has illuminated extensive suburban activity. The land outside the North Gate, flanking Dere Street – the road to the Roman frontier at Hadrian’s Wall – was particularly densely occupied. Rose Ferraby, Crown copyright and database rights 2018 Ordnance Survey

Indeed, although the mosaics in the southern townhouses speak of wealthy residents still being present in the later 4th century, it does appear that by then the good times were beginning to end. Some of Isurium’s public buildings, markers of the settlement’s civic status, appear to have gone out of use or possibly changed their purpose during this period: the creation of the town’s outermost ditch during enhancement of the defences cut through part of the northern seating bank of the amphitheatre, while a hearth was dug into the forum, possibly for ironworking – radiocarbon dating of its contents suggests that this was done c.AD 342-421.

What caused this decline in Isurium’s fortunes remains unknown; likewise, evidence for significant activity on the site in the immediate post-Roman period is very scarce, though, given the site’s useful location at the meeting of road and river, it seems reasonable that it would have remained at least locally relevant for some time. By the time the area became part of the 7th-century kingdom of Northumbria, though, the site had been eclipsed by the rise of new power centres, not least the foundation of St Wilfrid’s monastery at Ripon, just 10km away, in c.672. Yet it is through ecclesiastical echoes that we can still find hints of Isurium’s presence today: Aldborough’s village church stands in the middle of what was the Roman town’s forum, with its churchyard occupying the same level plateau that was created to host markets centuries earlier. While the extant church is 14th-century in date, it had a Norman predecessor. This latter construction could simply represent canny reuse of a conveniently flat area of land, exploiting a location that also boasted easy access to good building stone recycled from the Roman ruins, but might there have been an even earlier church on the site, part of a tradition of buildings memorialising the heart of what had once been an important urban community?

Isurium seems to have entered a marked decline. Some of its public buildings appear to have gone out of use, or seen changes of purpose – in this phase plan, we can see how a new defensive ditch to the south cut into the amphitheatre, putting it out of use. Rose Ferraby, Crown copyright and database rights 2018 Ordnance Survey

FURTHER INFORMATION

R Ferraby and M Millett (2020) Isurium Brigantum: an archaeological survey of Roman Aldborough, Society of Antiquaries of London, £35, ISBN 978-0854313013; a free online version is available at https://doi.org/10.26530/20.500.12657/37741.

Aldborough Roman Site, which includes a museum and mosaic house, is under the care of English Heritage. The site is currently closed for the winter, but for information on visiting next year, see www.english-heritage.org.uk/visit/places/aldborough-roman-site.


This article appeared in CA 369. Read more features in the magazine. Click here to subscribe

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