Introduction
Knocknashee is one of Ireland’s most remarkable prehistoric landscapes. Rising 272 metres above sea level in south County Sligo, its distinctive flat-topped summit contains one of the country’s largest concentrations of prehistoric monuments. Scattered across the plateau are two large cairns, the remains of more than fifty circular stone-built roundhouses and an extensive enclosure that has intrigued archaeologists for generations.
Although the archaeological significance of Knocknashee has long been recognised, many fundamental questions about the site remained unanswered well into the twenty-first century. When was the settlement occupied? How were the roundhouses constructed? What was the purpose of the enclosure? Despite decades of study, there was little scientific evidence to provide definitive answers.
Figure 1. The Northern Cairn on the summit of Knocknashee. In the foreground, a later dry-stone field boundary crosses the hill, illustrating the long history of human activity on the summit.
Between 2016 and 2021, researchers from Queen’s University Belfast undertook a programme of archaeological investigation that combined topographical survey, geophysical survey and targeted excavation. The results firmly dated the roundhouse settlement to the Late Bronze Age, provided new insights into its construction and development, and prompted a reappraisal of the enclosure surrounding the summit. Together, these investigations represent the most significant advance in our understanding of Knocknashee since archaeological research on the hill began.
Early Archaeological Research
Although Knocknashee had attracted archaeological interest for many years, it was during the second half of the twentieth century that the summit received its first detailed investigation. The hill’s remarkable concentration of prehistoric monuments, including two large cairns, numerous stone-built roundhouses and an extensive enclosure, had long been recognised, but without modern survey techniques or scientific dating, many aspects of the site remained uncertain.
A major milestone came in the 1960s when J. K. St Joseph and K. Norman carried out an aerial and field survey of the summit. Their work produced the first comprehensive plan of the site, recording the enclosure, cairns and numerous roundhouses, and established Knocknashee as one of Ireland’s most important prehistoric hilltop sites.
During the 1970s, Professor Michael Herity undertook a limited excavation of one of the roundhouses. Although the excavation demonstrated the archaeological potential of the site, the results were never fully published, leaving the date of the settlement and the relationship between its principal monuments unresolved.
By the early twenty-first century, archaeologists generally regarded the two cairns as Neolithic burial monuments, while the enclosure was interpreted as the earthwork of a Bronze Age hillfort. The chronology of the roundhouse settlement, however, remained uncertain. Advances in topographical survey, geophysical prospection and radiocarbon dating now offered the opportunity to investigate these questions using techniques unavailable to earlier researchers.
This led to a new programme of archaeological investigation, beginning in 2016, which would fundamentally reshape our understanding of Knocknashee.
The 2016 Survey
In the summer of 2016, researchers from Queen’s University Belfast began the first phase of a major archaeological investigation of Knocknashee. Rather than commencing with excavation, the team carried out a detailed programme of topographical and geophysical survey, allowing the archaeological landscape to be examined without disturbing the surviving remains.
Figure 2. Results of the 2016 topographical survey of the Knocknashee summit, showing the distribution of confirmed and possible roundhouses, the two cairns and the enclosing earthworks. The survey demonstrated the scale and organisation of the prehistoric settlement. Reproduced from Brandherm et al. (2018).
Using high-resolution topographical mapping, aerial photography, drone imagery, magnetometry and earth resistance survey, archaeologists produced the most detailed record of the summit ever undertaken. These surveys accurately mapped the earthworks, cairns, enclosure and roundhouses, while also identifying previously unknown archaeological features beneath the surface.
One of the project’s most significant achievements was the mapping of the prehistoric settlement. The survey brought the number of identified roundhouses to a minimum of fifty-one and possibly more than sixty, demonstrating that the settlement was considerably larger than previously recognised. The survey also revealed a previously unrecognised pattern in the distribution of the houses. Two principal concentrations were identified, referred to as the North Area and East/Southeast Area, separated by an approximately 40-metre-wide corridor largely free of structures. The researchers suggested that this may reflect the organisation of space within the settlement, possibly even providing a route through the summit, although its precise purpose remains uncertain.
The survey also identified areas for future investigation, leading directly to the excavation of three roundhouses during the following season. While the survey revealed the layout of the settlement, excavation would be needed to determine when the houses were built, how they were constructed and whether they had been occupied at the same time.
Excavating the Settlement (2017)
Building on the results of the 2016 survey, archaeologists returned to Knocknashee during the summer of 2017 to undertake the first modern excavation of the prehistoric settlement. Rather than opening large areas of the summit, the team targeted three adjacent roundhouses, Houses 18, 19 and 20, to investigate their date, construction and relationship to one another.
A single trench cut across all three structures revealed that the houses had been built using stone wall footings with earthen foundations. At least two had been constructed on deliberately prepared platforms, while House 20 preserved evidence of a carefully laid clay floor, demonstrating the considerable effort invested in their construction.
Although relatively few artefacts were recovered, the excavation produced fragments of coarse prehistoric pottery, flint and chert tools, ground stone discs and charcoal suitable for radiocarbon dating.Earlier activity on the summit was represented by residual lithic material, including a fine butt-trimmed flint knife considered likely to date to the Late Mesolithic. Its position within the roundhouse remains suggests that it had been redeposited long after its original use.
The excavation’s most important discovery came from the radiocarbon dates, which demonstrated that the settlement was occupied between approximately 1260 and 815 BC. This firmly placed the excavated roundhouses in the Late Bronze Age and showed that they were not contemporary with the nearby Neolithic cairns.
Figure 3.
House 18 under excavation during the 2017 archaeological investigations at Knocknashee. The surviving stone wall footing of the Late Bronze Age roundhouse is clearly visible. Photograph from Brandherm et al. (2020).
The investigations also raised questions about how the settlement was used. Of twenty roundhouses examined geophysically, only two produced magnetic anomalies consistent with hearths. Together with evidence that some houses were dismantled during prehistory, this suggested that the structures may not all have been contemporary or occupied throughout the year. Although only a small area was excavated, the work provided the first secure scientific dating of the settlement and greatly improved our understanding of its development.
Investigating the Enclosure (2020–2021)
While the 2017 excavation established the date of the settlement, the purpose of the enclosure surrounding much of the summit remained uncertain. Since the 1960s it had generally been interpreted as the remains of a Bronze Age hillfort, but this assumption had never been tested through excavation.
Archaeologists returned to Knocknashee in 2020 and again in 2021 to investigate the enclosure. Excavation trenches were opened across the eastern side of the feature to examine its construction, date and original function.
Figure 4. Remains of a prehistoric roundhouse on the summit of Knocknashee, with the Northern Cairn beyond. Knocknarea and Benbulben can be seen on the distant skyline.
The results challenged the traditional interpretation of the enclosure. In the excavated section, what had appeared to be an earlier earthen bank beneath a later drystone wall proved to be tumble from the wall resting on decayed limestone bedrock. A second feature on the lower terrace was interpreted tentatively as a relatively recent clearance bank associated with land improvement.The researchers nevertheless cautioned against extending these findings to the entire perimeter. Only a very small portion of the extensive system had been excavated, and further investigation would be required before a prehistoric origin for all of the banks could be ruled out.
The investigations also raised wider questions about why the summit was chosen for settlement. The two passage tomb cairns were already ancient monuments by the Late Bronze Age, and the researchers noted parallels with other hilltop settlements established close to earlier megalithic monuments. At Knocknashee, the two principal groups of roundhouses may even have had different visual relationships with the two cairns. The significance of this arrangement remains uncertain, but it suggests that the older monuments may have influenced how the later settlement was organised.
Conclusion
The archaeological investigations undertaken at Knocknashee between 2016 and 2021 represent the most significant research ever carried out on the summit. Combining topographical survey, geophysical prospection, excavation and radiocarbon dating, they have provided the clearest understanding yet of the site’s prehistoric occupation.
The investigations firmly established the roundhouse settlement as a Late Bronze Age community dating to approximately 1260–815 BC, while demonstrating that the settlement developed over time rather than representing a single phase of occupation. They also prompted a reassessment of the enclosure surrounding the summit, highlighting that its date and function remain open to further investigation.
Despite these advances, much of Knocknashee remains unexplored. Only three of the minimum fifty-one identified roundhouses have been excavated, while questions remain about whether all the houses were contemporary, whether occupation was permanent or seasonal, and what relationship the Late Bronze Age community had with the much older cairns.
As archaeological techniques continue to develop, future investigations will undoubtedly reveal more about this remarkable hilltop landscape. The research undertaken between 2016 and 2021 has laid a strong foundation for that work and marks an important milestone in our understanding of Knocknashee.
A Note on Visiting Knocknashee
The archaeological remains on Knocknashee have survived for thousands of years but are vulnerable to erosion and disturbance. Visitors are respectfully asked to avoid walking or climbing on the passage tomb cairns, and to avoid walking across the remains of the prehistoric roundhouses where possible.
Please enjoy the site with care and help ensure that these remarkable remains continue to survive.
Further reading
For further information on this subject, see the related material on the Achonry Mullinabreena Heritage & Culture website:
Sources and References
- Brandherm, D., McSparron, C., Kahlert, T. & Bonsall, J. (2018). ‘Topographical and Geophysical Survey at Knocknashee, Co. Sligo: Results from the 2016 Campaign’. Emania, 24, pp. 81–96.
- Excavations Bulletin. (2020). Knocknashee, Co. Sligo – Summit Enclosure Investigation.
- Excavations Bulletin. (2021). Knocknashee, Co. Sligo – Further Investigation of the Summit Enclosure.
- Brandherm, D., McSparron, C., Boutoille, L. & Kahlert, T. (2021). ‘Knocknashee – An Unusual Bronze Age Hilltop Settlement in South Co. Sligo’. Sligo Field Club Journal, Vol. 7.
- The Hill of the Fairies, Archaeology Ireland 32(3), pp. 30–33.
Acknowledgement: This article is based primarily on the archaeological investigations undertaken at Knocknashee by researchers from Queen’s University Belfast between 2016 and 2021. Their work has significantly advanced our understanding of the site and forms the foundation of this overview.
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