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Ireland's Hillfort Capital Yields Ancient Secrets
The Baltinglass hillfort cluster, sometimes referred to as "Ireland's Hillfort Capital," has long fascinated archaeologists with its exceptional concentration of prehistoric monuments. According to Phys.org, this remarkable landscape comprises up to 13 large hilltop enclosures spread across a necklace of hills at the southwestern edge of the Wicklow Mountains. The area demonstrates continuous use and monumental construction from the Early Neolithic through the Bronze Age, spanning approximately 3700 to 800 BC. Several hillforts, including Rathcoran and Hughstown, have Neolithic origins with banks first constructed in the fourth millennium BC, whilst others such as Rathnegree and Sruhaun were enclosed during the Middle to Late Bronze Age.
The Wicklow Mountains landscape where the Brusselstown Ring settlement was established. (J.-H. Janßen/CC BY-SA 3.0)
Within this extraordinary prehistoric complex, Brusselstown Ring stands apart. The site constitutes one of Ireland's largest hillforts, with two widely spaced ramparts encompassing a footprint of 41.19 hectares. Even more remarkably, the outermost enclosing element forms part of a much larger contour fort known as Spinans Hill 2, which encompasses both Brusselstown Ring and the neighboring Neolithic enclosure of Spinans Hill 1, creating a total enclosed area of 131 hectares. Dr. Dirk Brandherm, lead researcher on the project, noted that hillforts encompassing more than a single hilltop are exceedingly rare across Ireland and Britain, and uncommon even among the Late Iron Age oppida of continental Europe dating to 150-50 BC.
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Photogrammetry map of Brusselstown Ring indicating potential roundhouse footprints, test trench locations and the potential cistern (A), with close-up lidar image of house platforms (visible as circular footprints) on the eastern slope (B). (Brandherm et al. /Antiquity Publications Ltd)
Revolutionary Evidence of Dense Prehistoric Population
The sheer number of potential roundhouse footprints at Brusselstown Ring underscores the exceptional character of the site. Previous terrestrial survey work had detected 288 potential hut sites, but subsequent airborne surveys utilizing advanced photogrammetry and lidar technology identified more than 600 microtopographical anomalies consistent with prehistoric house platforms. These data revealed 98 potential roundhouse footprints within the inner enclosure, with a further 509 between the inner and outer enclosing elements. This discovery positions Brusselstown Ring as the largest prehistoric nucleated settlement by far in Ireland and Britain.
For comparative context, only a handful of other sites across the entire Atlantic Archipelago feature more than a few dozen roundhouse footprints, and not all of these possess enclosing elements. The next-largest roundhouse agglomerations at Turlough Hill in County Clare and Mullaghfarna in County Sligo feature approximately 140 and 150 houses respectively, yet both remain unenclosed. Within the Baltinglass landscape itself, the second-largest agglomeration of roundhouse footprints appears at the Neolithic enclosure of Rathcoran, with 124 potential hut sites.
Dr. Cherie Edwards, co-author of the study, emphasized the significance of these findings:
"Brusselstown Ring presents an intriguing case for understanding settlement dynamics in Ireland during the Bronze Age," she explained. "This site - along with a small number of other nucleated settlements situated on hilltops - appears to have emerged around 1200 BC. This pattern contrasts sharply with the more typical form of prehistoric Irish settlements, which generally consist of one to five dwellings."
Test Excavations Confirm Late Bronze Age Origins
During 2024, the research team initiated a program of test excavations targeted at a small sample of roundhouse platforms to address critical questions regarding the date, development, and function of both the enclosing elements and the internal settlement. The microtopographical anomalies detected ranged in diameter from 3 to 12 meters, with most falling within the 5 to 10 meter range, consistent with the dimensions of prehistoric roundhouses. Four test trenches were excavated at locations featuring anomalies of different sizes to investigate whether size differences might indicate functional or social differentiation.
All four tested anomalies produced compelling evidence of prehistoric occupation. Trench 1 revealed a layer of cobbles consistent with a floor surface, as well as evidence for a large burning event. Trench 3 uncovered part of a hearth feature surrounded by a series of stake holes, whilst trenches 2 and 4 produced evidence for pit features and additional potential stake holes. Although artefactual assemblages proved sparse (typical for Irish hillforts) they comprised a small number of lithics and some burnt clay fragments.
Most significantly, radiocarbon dates situate the occupation of the site primarily in the Late Bronze Age, between 1210 and 780 BC. Additional radiocarbon dates from a stake hole and a pit infill from trench 2 also indicate use of the house platform during the Early Iron Age, spanning 750 to 400 BC. Dr. Edwards elaborated on the social implications of these findings.
"Radiocarbon dating results demonstrate that houses of all sizes were occupied contemporaneously, and no discernible differences were found in the artifactual assemblages associated with each structure. Although preliminary, these findings align with broader patterns observed at other Bronze Age domestic sites in Ireland, which similarly lack material evidence for wealth differentiation or social hierarchy."
Aerial view of the potential cistern, in the foreground of the image (A) and a view from its interior showing a line of kerbstones (B) . (Brandherm et al. /Antiquity Publications Ltd)
Additional survey work undertaken alongside the test excavations allowed better characterization of previously identified features, including a boat-shaped structure with a level interior situated near trench 4. The boat-shaped outline proved inconsistent with a prehistoric roundhouse, and the stone blocks defining its perimeter were considerably larger than those usually associated with roundhouse footprints at the site. Earlier survey work had recorded a small stream of water running into the interior of the structure, seeping from the foot of a rocky outcrop further up the slope.
The shape and dimensions of this structure are consistent with Bronze Age and Iron Age cisterns known from other parts of Europe. If the number of roundhouse platforms identified at the site can be taken as indicative of population density, some provision to supply the resident population with clean water should perhaps be expected. If further excavation confirms that this structure functioned as a cistern, it would represent the first known feature of its kind from an Irish hillfort, raising profound questions about the extent and nature of communal infrastructure in the settlement and the level of coordinated planning required to meet the needs of the populace.
The preliminary results from this ongoing fieldwork suggest that at least a substantial proportion of the more than 600 microtopographical anomalies identified by topographical surveys represent genuine prehistoric house platforms. The available evidence indicates their occupation mainly during the Late Bronze Age, with continued use or reuse of some house platforms in the Early Iron Age. Dr. Edwards addressed the site's chronological trajectory:
"The site's chronological trajectory aligns closely with that of other, albeit smaller, hilltop nucleated sites in Ireland, implying that its abandonment followed a broader regional pattern of gradual decline during the Iron Age, around the third century BC. This decline also appears unrelated to the climatic shift toward cooler and wetter conditions that began during the Bronze Age–Iron Age transition, circa 750 BC."
Future work will focus on confirming the nature and date of the potential cistern, identifying structural features of the prehistoric roundhouses, and establishing the nature and chronology of the enclosing elements. These investigations promise to shed further light on this remarkable settlement, which stands as a testament to the organizational capabilities and social complexity of Bronze Age communities in Ireland, challenging our preconceptions about prehistoric societies and their capacity for large-scale communal living.
Top image: Detailed view of the prehistoric settlement remains at Brusselstown Ring. Source: Brandherm et al. /Antiquity Publications Ltd
By Gary Manners
References
Brandherm, D., Edwards, C., Boutoille, L. and O'Driscoll, J. 2025. Brusselstown Ring: a nucleated settlement agglomeration in prehistoric Ireland. Available at: https://www.cambridge.org/core/journals/antiquity/article/brusselstown-ring-a-nucleated-settlement-agglomeration-in-prehistoric-ireland/C02CF0872F44AB918303D2A0474C9F9E
Science X Network. 2025. Scientists have uncovered evidence of Ireland's largest prehistoric hillfort settlement. Available at: https://phys.org/news/2025-12-scientists-uncovered-evidence-ireland-largest.html
