Crannógs in County Offaly. By John Dolan

While Offaly has a huge range of Early Christian church and monastic sites it would not have been noted for crannogs, unlike its neighbour in Co. Westmeath.  Surprisingly, Offaly has 13 crannog sites recorded in the National Monuments database, however they are in many ways different from the usual picture of the small, man-made island in a lake. Many of these crannogs are located close to natural esker and drumlin routeways and survive as wetland settlements in or close to bogs.  One third of Offaly is covered by peatland.

Crannogs in Ireland.

The name crannog is obviously the Irish names of ‘crann’ for tree and ‘óg’ in this case referring to small and not young.  But we will see that ‘small tree’ does not account for the size and scale of wood used in the construction of these lake dwellings which are generally in open bodies of water.

There is no agreed figure for the number of crannogs in Ireland.  Some have suggested 1,200 over the whole country while others take the number over 2,000!  Crannogs were constructed in the sixth and seventh centuries and occupied and used up to the end of the seventeenth century.  As a monument in the landscape that has changed considerably with the reduction in water, lake and river levels, along with the drying out of the bogs since the Middle Ages, it is only by accident that a new crannog is discovered.

Dried out lake with crannog, Lough Gara, Co. RoscommonDried out lake with crannog, Lough Gara, Co. Roscommon

The earliest recorded account of a crannog was in 1784 in Galway.  Records in 1809, 1812 and in the 1830s were followed by specific references in Samuel Lewis’ Topical Dictionary of Ireland.  In the 1860s William Wilde described crannogs as ‘drowned islands’.

Whereas north Leinster is more suited to crannogs on open water, in Offaly water bodies were found in bogs or had a limited dry lake shoreline to site a crannog. Some would have required a boat or a long walk through marshland to access.  O’Sullivan finds that some crannogs were sited in close proximity to large, royal ringforts.

Crannog and related RingfortCrannog and related ringfort

Along with Ogham Stones, High Crosses and Round Towers we find 347 crannogs in Scotland but only one at Llangorse Lake in Wales.

Distribution map of Irish Crannogs

Distribution Map of crannogs in Ireland.

Map of Crannogs in Offaly

Offaly’s crannogs stretch across the midlands from south of Daingean to the River Shannon with one in the south of the county just east of Leap Castle.

Map of Offaly Crannogs

Previous Investigations.

As landlords carried out land drainage schemes in the early nineteenth century an increasing number of archaeological sites were revealed, including in the raised bogs of the midlands.  The Commission for Arterial Drainage and Inland Navigation was an ambitious program of drainage works between 1843 – 1852, about 25 crannogs and 377 objects were discovered, mostly in Roscommon and Leitrim but also in Cavan, Monaghan, Limerick, Meath, Westmeath, Down, Tyrone and Offaly.

This program exposed an increasing number of archaeological sites.  Wilde included many items recovered from crannogs in his Catalogue of Antiquities for the RIA in 1857. In 1886 William Wood-Martin published the first book on crannogs with his The Lake Dwellings of Ireland, based mainly on the notes of William Wakeman.

The Irish Archaeological Wetland Unit was established in 1990, based at UCD.  It was tasked with systematically surveying the threatened raised bogs in the midlands areas.  Less then 10% of these bogs remained intact, the remainder had been extensively altered by ongoing drainage and peat harvesting.

Within four years it had completed surveys of the major bogland areas in seven counties and had undertaken three separate excavations on three threatened wetland sites in Offaly, Mayo and Sligo. Its major excavation was at the Bronze Age settlement crannog at Clonfinlough, Co. Offaly (see below).

Ballinderry, Co. Offaly.

There is a Ballinderry located in Counties Wicklow, Galway, Derry, Antrim, Tyrone, Meath, Tipperary, Kildare, Westmeath and Roscommon according to

The Ballinderry crannog in Co Offaly has been mentioned in a previous blog with a focus on the Viking material found during the famous excavations by H. O’Neill Hencken of Harvard and published in 1935 and 1942.  The Harvard program had a significant impact on the quality of crannog and archaeology research in Ireland in general.  More recently the Hencken archive has been examined by Conor Newman, NUIG with particular emphasis on the earlier periods of habitation at Ballinderry 2.

A small island on the lake in Ballinderry Lough was occupied on a number of different occupations over time.  There is evidence that the water levels in the Lough rose and fell on a number of occasions.  The earliest human evidence was in the Late Bronze Age and probably dated between 400 – 100 BC.

The crannog was discovered when Ballinderry Lough and nearby Moyvoughly Bog were drained around 1847 to facilitate the building of the Midland and Great Western railway from Mullingar to Athlone. The drainage has substantially altered the lake since prehistoric time as the maps show below.

However, between 1847 and the 1880s the crannog was regularly pilfered for bones and artefacts leading to some items being unrecorded.

(The following maps show the early OS editions on the left hand side with the current digital maps on the right hand side The site of the crannog is inside the red circle.).

Ballinderry Lough pre-railroand and current digital mapBallinderry Lough pre-railroad and current digital map.  Note how much the lake has diminished since the building of the railroad.

Newman sketches out four phases of occupation.  Initially, two rectangular structures were built in the Later Bronze Age but subsequently abandoned. Then the circular wicker ‘huts’ were built on top of the previous rectangular structures. Subsequently large amounts of stone and brushwood were laid over the wicker ‘huts’. The main function of these wicker ‘huts’ is still unclear, perhaps storage or pens for small animals or perhaps smoke-houses. Finally, the crannog was built during the 8th century AD on top of the layer of stone and brushwood. The perimeter of the crannog was marked out with a palisade of oak posts.

Ballinderry Wicker HutsBallinderry Wicker Huts. (Reproduced from Hencken, Proceedings of the Royal Irish Academy: Archaeology, Culture, History, Literature Vol. 47) 

The main feature of the crannog is a rectangular building to the west close to the group of ten circular wicker ‘huts’. A large hearth was placed outside the perimeter of the crannog.

Piles at base of crannog

Piles at base of Crannog. (Reproduced from Hencken, Proceedings of the Royal Irish Academy: Archaeology, Culture, History, Literature Vol. 47)

Finds.  These finds are the largest and most varied from any Irish site for this period. There are 10 bronzes dated to about 700BC that include tools and ornaments.  There was a huge quantity of pottery, about 300 sherds in all. A number of stone tools were also recovered along with several pieces of iron.

Of particular interest was a large dugout boat that was recovered, the size of this boat suggests that it was larger than required just for the lake at Ballinderry and may have at some time been used in the nearby Brosna or Shannon rivers.  Other dugout boats have been found at crannogs in Westmeath and Meath.

Dug out boat at Ballinderry crannog

Dug out boat at Ballinderry crannog. (Reproduced from Hencken, Proceedings of the Royal Irish Academy: Archaeology, Culture, History, Literature Vol. 47) 

Around 620lbs of bone has been found associated with the Bronze Age occupation.  Species include cattle, pig, sheep/goat, horse, red deer, badger, otter, crane, wild duck and cat but no trace of dog.  Meat was clearly an important part of the diet.  The volume of deer bones also suggest that deer hunting may have been carried out locally.

Three human skulls were found at the base of one of the layers. These skulls probably relate to the European Celtic ritual of the treatment of the dead.  They may represent a ritual deposit, such as a foundation sacrifice.

Skull cults appear across history and even in some modern tribal societies. Skulls have been found at crannogs in Offaly and other sites in the midlands, particularly in the crannogs at Lough Gara between Sligo and Roscommon.  The display of the skulls of your enemies is well recorded across Celtic Europe, particularly at the Entremont oppidium in southern Gaul.   The Irish account of this skull culture is best recorded in the activities of Cu Chulainn in the TÁIN BÓ CÚAILNGE

Sherds of high value E-ware pottery, a blue glass bead and an enamelled pin were found in the wicker ‘huts’. E-ware pottery is wheel-thrown and is imported from western France.  E-ware is generally only found in high status sites.

The high quality of the pre-crannog material is impressive and testifies to the high rank and wealth of those who lived and visited at the Ballinderry lakeside and their conspicuous consumption. This is confirmed by the quality and volume of the later Viking finds already discussed in the earlier blog.

bronze brooch and Pewter Ring brooch

Bronze brooch and Pewter Ring brooch


The Annals of the Four Masters refer to a crannog at Clonmacnoise in the floodplain. Stokes wrote in 1890 that ‘the heathens and rabble were living in the island that was upon it.  And the shouting and noise of that unprofitable folk used to disturb the clerics. Ciarán entreated the Lord that the island might be moved out of its place, and that thing was done; and still for remembrance of that miracle is seen the place wherein the island was in the lake’.   The area was ploughed in the 1950s and uncovered oak timbers and an early medieval iron tongs which is housed in the National Museum in Dublin.

Clonmacnoise crannog

The crannog at Clonmacnoise in the flood plains of the Shannon


Clonfinlough crannog is located close to two of the major highways of prehistoric Ireland – the Shannon and the Eiscir Riada. It has also been called Fin Lough in texts and on maps. A crannog was discovered on its western shore in 1884.  The site was revealed at a depth of 2‐3m in bog, and was found due to peat extraction.

Clonfinlough is somewhat different to other lake dwellings and does not appear to have stood in open water. The enclosure encompassed three platforms which represented two substantial hut sites and one smaller hut site. Dendrochronological analysis of timbers from this site indicate that the construction and occupation of the site took place from 917‐886 BC, perhaps representing one or two generations of an extended family.

Reconstruction drawing of Confinlough settlement

Reconstruction drawing of the Clonfinlough settlement. (Reproduced from the former Irish Archaeological Wetland Unit, UCD)

Finds included six coarseware pottery, saddle querns and bones from cattle along with small amounts of sheep and pig. Two amber beads were recovered from the site. Having probably originated in the Baltic or possibly brought from the eastern coasts of Scotland or England, amber was a highly prized material, and its existence at such a site would serve as an indicator towards trade and communications.

The excavation revealed a type of house never previously recorded and has given a new insight into settlements in the Late Bronze Age.  Wooden tubs, troughs, bowls, spoons, ladles, and two wooden paddles were found.  The wooden paddles (primitive oars) are 2.7 metres long and were used for propelling or steering a large craft on water.

Waterlogged remains of a Bronze Age house, Clonfinlough, Co. Offaly

Waterlogged remains of the Bronze Age house

Clonfinlough map

Clonfinlough map, note the absence of water in the modern digital map.

The ‘Clonfinlough Stone’ is a glacial erratic limestone boulder decorated with a series of cruciform figures, incomplete T‐shaped figures, a possible representation of a footprint and several longitudinal and transverse joints.  The stone cannot be linked archaeologically to the crannog.

Clonfinlough Stone

Clonfinlough Stone

Annaghmore Lough or Lough Annagh

This is a case of another disappeared lake called Annaghmore Lough.  Somewhat confusingly, in the literature it is named as both Annaghmore Lough and Lough Annagh.  In addition, this crannog is not included in the National Monuments database for Co. Offaly.

Lewis’ Topographical Dictionary of Ireland mentions various houses in Lough Annagh. Co Offaly.  He records that ‘in the middle of this lake… there is a traditional report that in the war of 1641 a party of insurgents had a wooden house erected on this platform, whence they went out at night and plundered the surrounding country’.  This was confirmed in 1868, when seventeenth century armour, an iron halberd, iron swords, a matchlock and a gun-barrel of small calibre were some of the finds made on an ‘island-like patch rising a little above the water level, of piles’.

Annaghmore Lough

Annaghmore Lough/Lough Anna. Note the effect of land drainage.

There are a few reports of two crannogs in Lough Annagh. However, a General Dunne of Brittas Castle, Clonaslee wrote a letter to Rev. J Graves which was read at a meeting of the Historical and Archaeological Association of Ireland held in Kilkenny on 21st October 1868. Gen. Dunne describes Lough Annagh as between King’s and Queens counties,  one mile long and about half a mile broad.  He writes ‘in it are two Cranoges’. He describes the finds as ‘several querns, bones and four boats hollowed from logs of timber, found in the lake’.   Later, ‘some boys picked up in the lake near one of the Cranoges, an iron cuirass, a sword and other arms’. One of these boats was subsequently gifted by Gen Dunne to Mr. T L Cooke of Birr.

Dunne suggests that a battle between James and William’s armies (1691) involving some hundreds of troops occurred on a hill overlooking the lake and that some troops fleeing the battle took shelter on the crannog, that this accounts for the arms found on the crannog and in the lake.

Rev. Graves recounts that on a return journey from Clonmacnoise via Tullamore he called into a Mr. Atkins, jeweller in that town. Mr. Atkins had acquired over twenty items found at the lake including a matchlock barrel, gun barrel, pistol barrels, cuirass breastplate, iron halbert and a variety of other items.  While still in Tullamore Rev. Graves visited a Mr. Thomas Stanley who subsequently wrote a detailed letter to him. Mr. Stanley recounts hearing about the finds, visiting the lake, acquiring a boat and getting into the water beside the island. He calculated that there were 120 wooden piles in the water, arranged in lines and that each pile had a diameter of about five inches.

Ballykean Bog, Walsh Island.

Discovered by the IAWU in their 2003 survey. The first excavation was carried out in summer 2007 and revealed a figure of eight house, along with substantial remains in the bog. The site was surrounded by a palisade, sometimes by a single row of posts, other times by a double row.  A second excavation was carried out in the summer of 2009.  The crannog has been dated to 600-700AD.  Ballykean crannog was situate over 500m into the bog with no evidence of a contiguous body of open water.

The house was small, 9m in diameter. A central, rectangular hearth was in the main part of the house containing an amount of animal bone found within the charcoal. Around the hearth was a wooden floor made from regularly laid roundwoods, jointed and pegged in place.  The house had internal components indicated by rows of stakes, a double external wall and entrances to the east and west.

A variety of artefacts, mostly domestic in nature, were recovered from the site. Amongst these was a range of wooden items, including an oar, a spatula, a small box, a decorated comb, handles, needles and several miscellaneous items. The leather items discovered included several well-preserved shoes. Organic remains recovered included a quantity of animal bone from around the hearth, as well as deposits of fruit stones and seeds.

Ballykean crannogBallykean crannog

Hawkswood Crannog

This crannog is in Clonad Wood, south of Tullamore.  The entry in the national Monuments database reads ‘Situated on wet poorly drained bogland. Outline of circular shaped tree-planted area (approx. diam. 60m) at W end of coniferous tree plantation visible on Digital Globe aerial photograph taken 20/03/2019. Circular grove of trees standing on bogland to the W of Derrynaslingue wood depicted on revised ed. OS 6-inch map’.

Hawkswood townland, south of TullamoreHawkswood crannog