Chapelizod Heritage Association Podcast

21. Knockmary Cist (Cromlech)


21. Knockmary Cist (Cromlech)


Chapelizod only appears in documentary sources from around the early 13th century CE, but the archaeological remains of the area point to human activity in the Liffey Valley from the depths of Irish prehistory. The most significant – and earliest – archaeological site in the area of Chapelizod is the Knockmary Cist or Knockmary Cromlech, located at the summit of Knockmary Hill where it holds a commanding view of the village and surrounding landscape.

You can find the site by entering the Phoenix Park through the turnstile at the top of Park Lane. Continuing straight ahead, you follow the narrow path to the top of the hill. Cross the road, and continue up the driveway. Go right along the hedge at the top, and you will come upon the remains of the cromlech (pictured above). Today, all that can be seen at this site on the small hill above Chapelizod are five upright stones supporting a large capstone. Once upon a time this assemblage of stones served as the rock chamber of the tomb – the remains of which are often known as a dolmen or cromlech. They would have been covered in a mound of earth; some accounts describe the original mound at Knockmary to have had a height of 15 feet and a diameter of 120 feet (Borlase, 1897).

The largest stone measures roughly six foot six inches at its longest point. This capstone is made of calp, also known as “black quarry stone”. Later in time, this type of rock was commonly used for building works, and can be found incorporated into many of Dublin’s buildings; but this particular example is believed to have been dredged from the bed of the Liffey and brought up to this hill overlooking the valley (Borlase, 1897). It is supported by five smaller upright stones, creating a hollow void in which human remains and grave goods were deposited. The remains of three men were found inside this chamber when the mound was excavated in 1838. Numerous artefacts were also recovered: a small flint knife and a necklace of small sea-shells, perforated with small holes and strung together with a vegetal fibre that may have been seaweed. Four highly ornamented ceramic urns were also discovered in the mound, placed individually in their own small stone-lined chambers.These date to a later period in Irish prehistory – the Bronze Age. Whereas the bodies placed within the main cist at the center of the monument were buried whole, the urns contained the ashes of burned human bone. This represents a shift of not only technology, but also burial practices and perhaps religion between the Neolithic and the Bronze Age.

The story of the Knockmary Cist’s discovery is closely tied to the emergence of archaeology from antiquarianism in the 19th century. Even up to the 1960s the site was associated with the semi-mythical earliest colonists of Ireland, the so-called Fir Bolgs:

“The first people assumed to have dwelt in this country are the Firboigs, a pasture loving race, who inhabited Ireland about two thousand years ago. This deduction was made from the discovery of two Cromlechs in the nineteenth century, one on Knockmary Hill, overlooking Chapelizod, and the second in a sandpit near the village.” (McAsey, 1962, 37)

Two centuries earlier the interpretations were a lot more fanciful, based on the theory that stones such as this served as the altars or temples of Druids. This idea was only challenged in the mid-1800s, when empirical evidence was being sought to discover the true function of these mysterious monuments. In 1837 a man named George Petrie pioneered this work at the archaeological landscape at Carrowmore, County Sligo – the largest cemetery of megalithic tombs in Ireland. The results of this were presented to the Royal Irish Academy in 1838; the same year that Thomas Larcom, then director of the Ordnance Survey of Ireland, wrote to Petrie notifying him of the newly discovered site in the Phoenix Park. Full details on the context surrounding Petrie’s work in Carrowmore, the excavation of the Knockmary cist and the shift towards archaeological methods in Ireland can be found in the excellent article by David McGuinness (2010).

The remains of a second dolmen, originally located close to that on Knockmary Hill, can today be found in the tapir enclosure of Dublin Zoo.


Macalister  (1912)

Macalister  (1912)

Further Reading:

David McGuinness (2010) "Druids' altars, Carrowmore and the birth of Irish archaeology." The Journal of Irish Archaeology, Vol. 19, 29-49.

William Copeland Borlase (1897) The dolmens of Ireland, their distribution, structural characteristics, and affinities in other countries; together with the folk-lore attaching to them; supplemented by considerations on the anthropology, ethnology, and traditions of the Irish people. Available to read here.

Robert Alexander Stewart Macalister (1912) Ireland in pre-Celtic times. DublinMaunsel and Roberts. Available to read here.

Carmel McAsey (1962) "Chapelizod, Co. Dublin." Dublin Historical Record, Vol. 17, No. 2, 37-53.

Wm. Thompson, Robert Mallet, Samuel Ferguson, Professor Kane and Mr. Petrie (1838) "May 28, 1838." Proceedings of the Royal Irish Academy, Vol. 1 (1836 - 1840), 177- 191.