Ireland’s Crannóga

Crannóg Craggaunowen
Craggaunowen Project, The Crannog Adrian King / CC BY-SA 2.0

Crannóga were usually hidden away on islands constructed with solid oak.  One of the earliest excavated crannoges in Ireland was at Lagere near Drunshoughlin in Co. Meath.  The Four Masters described the destruction of a crannoge  during AD 933.  Turlough O ‘Conner escaped in 1246 from a ‘crannóge’  thus suggested it was in use as a prison.  Teigue O ‘Rourke was drowned while he crossed over to a crannoge.  Those dwellings were used as defensive systems up to as late as the sixteenth century. (Extracts from Cusack Margaret Ann’s Chapter XV in An Illustrated History of Ireland 1868)  [i]

The construction of crannóga began as large upright wooden posts (shaped at one end) were lowered into a lake then hammered deep into the mud.  For the inland area larger rocks, broken brushes or peat were used as fillers.  In the interior the creation of a floor of sand with pebbles were possibly strewn with reeds or straw.  It resulted in a circular enclosure of tightly spaced poles in the water with the tops visible above the water.  A dependence on local reserves or requirements aided the erection of a crannoge to a diameter of thirty-five metres.   Several of the larger dwellings were surrounded by timber or stone kerbing at the water’s edge with a palisade painted with white lime possibly during the sixth or seventh centuries.  To access the crannóga in several areas a path was constructed under water, in a circuitous path rather than a direct route to the island.  In several islands: causeways of stone or turf was constructed.  Other dwellings required a boat for access. (Crannóg The Island Lake Dwelling of Celtic & Medieval Ireland 16th February 2017[ii]

The term crannóg referred to an artificial island built on a lake.  Several were the oldest dwellings within prehistoric Ireland.  The name crannog was first referenced in thirteenth century documents.  The word ‘crann’ means ‘tree’ while ‘óg’ is miniature or young.  Crannóga were developed as a peculiar type of dwelling by Ireland’s early inhabitants.  Archaeological excavations have uncovered evidence that several were used as special places for metal work, fishing, or as hunting stations.  They may have been a ritual deposit location for sacred objects or weapons.  Crannóga dated from the Mesolithic era through Neolithic, Bronze & Iron Age: they continued onto the Medieval or Early Christian era.  Several homesteads were inhabited on these islands during the late Bronze Age or as late as the seventeenth century.  Various types of crannóga included: A cairn or mound crannog in Ireland.  The former were constructed of groups of piled stones while the mound was constructed with organic material of large tree trunks, large branches, marl or blue clay that were piled up into a mound.  In later times another type was built with tree trunks driven into a lake in an upright position then a platform was placed on top.  Roofs of the dwellings were made of wooden beams that met in the centre then were tied together with willow branches.  A thatch was constructed from reeds for the top.  [iii]

Several crannóga would have been surrounded by a palisade of wooden stakes as may be viewed at the reconstruction at Craggaunowen.  Islands were circular though several were elongated such as at Moynagh in Co. Meath.  Several of these islands were connected to the mainland by causeways that were visible above the water or slightly submerged.  The paths were known only to the local inhabitants.  Several islands were accessed by boats.  Lough Gara in Co. Sligo has the highest concentration of these lake dwellings within Ireland.  In Co. Sligo the average artificial island measured twenty-five metres in diameter.  They may have reached a height of 1.5 metres above the lake-bed.  Photos with a video of the Craggaunowen reconstruction of a crannog feature on this site. (Colm Sweeney 13th July 2013[iv]

The word ‘crannogs’ meant ‘young trees’ they were used as dwelling places within Ireland from the time of The Tuatha De Danann up to the seventeenth century.  These were defensive buildings where one had to cross a narrow causeway that connected the island to the mainland.  In several areas the path to the island was slightly submerged for security reasons.  Larger crannóga often had defensive positions with networks of tunnels beneath them, ‘labyrinths’ almost with protective ‘creeps’ or stile-like obstacles.  Engraved magical ogham stones were used as roofing material to support the tunnel walls.  Crannóga were quite large perhaps twenty-five meters in diameter, raised almost two meters above the surface surrounded by a wooden palisade wall.  Buildings within would have been made of wood & wicker as well.  Several settlements had livestock inside for protection from raiders.  An image of the Craggaunowen reconstruction of a crannóg may be viewed on this site.  [v]

Crannóg islands were constructed into a round shape with a few elongated like the Moynagh crannog in Co. Meath. Crannóga were developed during the Iron Age & Early Christian era.  Several homesteads were inhabited on these islands during the late Bronze Age or up to as late as the seventeenth century.   [vi]

Crannóga were constructed on islands, covered with trees during the Bronze Age to the early Medieval period.  The dwellings were built in shallow waters with timber, stones or various materials. The surrounding water acted as a defence to the occupants.  Several crannóga were inhabited up to the seventeenth century. Images of Crannogs at Tullylough, Co. Roscommon also Kilcorrran, Co. Monaghan by Con Brasnon feature on this page.  [vii]

The term refers to crannóga as artificially man-made islands constructed above water levels for safety of habitation.  They were constructed from driven rings of closely set wooden rings deep into the mud of lakes.  Layers of timber, brushwood or peat were laid down within a palisade.  Access to the crannóga were by artificial causeways or by boat.  They were mostly constructed in south Ulster or the Midlands.  Believed to have dated from the Early Medieval period.  The site at Newtownlow in Co. Westmeath was excavated during 1982-1989.  John Bradley excavated the Lough Moynagh crannóg (discovered in 1977) during 1980.  Images feature on this site by Con Brogan.  [viii]

They are approximately one thousand two hundred known crannóga constructed on shallow waters perhaps up to hundreds of yards from lakeshores.  According to O ‘Sullivan there may be ‘hundreds, if not thousands’ yet to be discovered or recorded also he stated that crannógs were centres of craft, industry, farming besides residences.  By the ninth & tenth centuries they were assemblies or feast locations for royal residents.  The highest density of these dwellings may have been located at lake-land regions of the north & west also across drumlin belts of the south midlands.  The word comes from the Irish ‘crannóc’ that means a small island built with young trees.  These were stone cairns & earthen mounds around lake shores. Possibly the crannóga were constructed during the sixth to seventh centuries.  Excavations were undertaken during the nineteenth century: antiquarians William Wilde, William Gregory Wood-Martin also William Wakeman excavated several sites.  Between 1839 & 1848 Wilde recorded discoveries by labourers at Legore Crannóg in Co. Meath: he attested that that site was possibly populated from the sixth to the eleventh centuries.  Moynagh Lough in Co Meath excavated by John Bradley was inhabited for at least two hundred years.  There have been reconstructions of crannóga at the National Heritage Park in Ferrycarrick, Co. Wexford, at Craggaunowen, Kilmurray, Sixmilebridge Co. Clare also at the Ulster Folk Park in Omagh Co. Tyrone.  A reference to archaeologist O’Sullivan Aidan’s Crannogs: Lake Dwellings of Ireland appears on this site. (The Irish Times 24th March 2001[ix]

Crannóga were created as manmade islands situated within shallow parts of lakes.  Co. Monaghan has an abundance of these lakes with several dated from 400 AD to 1600 AD.  Initially they were constructed for defensive habitation later they were a sign of local chieftain’s importance.  Interesting artifacts discovered during excavations now are housed within the National Museum: they included the following: a child’s & adult’s shoe that had been produced from stitched leather & heavily decorated combs of bone.  Needles had been made from bone or antler.  Images of artifacts feature on this site.  [x]

Several crannóga within Co. Mayo include settlements at Rooskeybeg, Drumady Lake also possibly two sites at Mayfield Lake.  [xi]

Crannóga were artificially constructed islands on turloughs, lakes or inland waterways.  The term derived from the Gaelic word ‘crann’ that meant ‘tree’ & ‘óg’  i.e. meant ‘young.’  This also referred to the large amount of timber used in the construction of the surrounding palisade. (Corlett C. 2001)  Moher Lake crannóg was constructed on a pile of large stones with the edge bordered by an enclosed wall: not more than three courses in height externally but the interior had scattered stones.  A man-made stone-lined dock of eight metres in length also two metres in width was in the south east section according to Morahan. (2001)  Crannóga were inhabited from the Bronze Age into the Medieval era.  Abundant historical or archaeological evidence exists of settlements on lake systems throughout Ireland. (O ‘Sullivan 1998[xii]

Lough Lannagh’s crannóg in Castlebar in Co. Mayo was called Clann Cuan, Fir Thíre or Fir Siúire, Claenloch also Mc Donell’s island or Boyd’s island in early eras.  The settlement was attacked several times.  Extensive information may be viewed at this link. (Brian Hoban[xiii]

Images of a possible crannóg features in the article by Jack Power in  The Irish Times 3rd February 2020.  Site was discovered on the seashore by Jimmy Ó ‘Céide following Storm Brendan.  Archaeologist Michael Gibbons stated that the crannóg was possibly dated from 4000 to 6000 years ago.  Perhaps the area was a lake during that timeframe.  [xiv]

Crannóga were ancient Irish lake dwellings constructed on artificial islands where dwellings or crannóga were built with layers of material such as mud, brushwood or stones.  They were set inside a palisade of wooden stakes closely set-together that consolidated the structures.  It acted as a defensive barrier. There are twenty-three recorded surviving crannóga within County Clare.  [xv]

Island dwellings dotted around Ireland & Western Scotland were known as crannogs.  The name itself may have derived from the old Irish word ‘crannóc.’  Several images of Scottish crannogs are featured on the site.  [xvi]

Artificially constructed islands provided sites for settlers homes on shallow lakes or islets.  Crannóga were fortified by single or double stockaded defences from the Late Bronze to the European Middle Ages.  An image of the Scottish Lough Tay crannóg features on this site.  [xvii]

Crannóga were lake forts erected upon logs embedded in the lake bottom.  Produced with wooden materials the forts provided protection to inhabitants during attacks.  Cranónga were fortifications in oriel prior to & during the Macmahons reign.  This site has a Barlett map of the Battle of Monaghan town also Rooskey Lake crannóg: stronghold of Dartry Mac Mahon by Grace Maloney 2002 & one of the Farney Mc Mahon Tribe.  [xviii]

Crannónga in Ireland was a partially or entirely artificially islands constructed on a lake.  The actual Irish word was derived from old Irish ‘crannóc.’  Following information may be relevant that: crannóng may be related to ‘structure / piece of wood’, ‘vessel / box / chest’, a’ driver’s box on a coach,’ ‘pulpit’ ‘wooden pin’ or indeed a ‘crow’s nest.’   Lake dwellings existed on this island from 4500 BC.  Evidence of an Irish crannóg from the Middle Bronze Age of 2000-600 BC referred to Ballinderry crannóg. Several excavations were uncovered within Ireland from the ‘missing’ Iron Age.  Approximately one thousand two-hundred examples exist within Ireland.  The largest concentration of Ireland’s crannóga are located within the drumlin belt of the midlands, northwest also up north.  Crannóga were constructed with wood to form a circular enclosure on a shallow rise on lakebeds.  This was surrounded by a circle of wooden piles with axe-shaped bases driven into the lake bottom.  A submerged causeway would have enabled local access to the islands or in some cases the use of logboats or coracles would have been required.  Several crannóga acted as ‘strongholds’ for the elite societies i.e. the O ‘Boylan’s or Mac Mahons within Co. Monaghan or Oriel up to the seventeenth century.  Reconstructions of crannóga are in situ at the National Heritage Park in Co. Wexford, at Craggaunowen, Co. Clare also at the Ulster Folk Park in Omagh Co. Tyrone.  An image of Loughbrickland crannóg in Co. Down inhabited by the Magennis family during the seventeenth century is featured on this site.  [xix]

Unique illustrations of crannóga by the British Queen’s mapmaker Richard Bartlett provided the only contemporary glimpse into this long-standing tradition.  He spent three turbulent years in Ireland from 1600-1603 for English troops as he surveyed the countryside.  His depictions of English troops as they attacked a crannóg are the only surviving images known. (Dr Robert Lenfert)) [xx]

Artificial islands known as crannóga were dotted throughout Ireland.  It had been believed that they were constructed during the Iron Age (800-43 BC) but a new paper in the Antiquity Journal by Duncan Garrow associate professor of archaeology at University of Reading (co-author of the article) revealed that they were constructed over five thousand three hundred years ago.  Maps with several images of Scottish Crannóga feature on this site. (Erin Blakemore 12th June 2019[xxi]

Lawless Christy, O ‘Flainn Ragnall, Baillie Michael & Brown David  December 1989 ‘Lavillenrie Crannóg an Early 7th century lake dwelling in Co. Mayo’ Cathair na Mart Journal of Westport Historical Society vol 9, No 1 (pages 21-25) (30th March 2023 NBC)

Mc Donald Theresa’s 1997 (new ed. 2006, edited by Jim Higgins) Achill Island Archaeology-History-Folklore referenced crannóga (Turner Print Group Longford) (NBC)


[i] Irish Crannógs ( [Assessed 6th March 2021]

[ii] Crannóg ( [Assessed 7th March 2021]

[iii] The Crannóg ( [Assessed 7th March 2021]

[iv] Ibid

[v] Crannógs ( [Assessed 7th March 2021]

[vi] The Crannóg ( [Assessed 7th March 2021]

[vii] Crannógs / Crannóga ( [Assessed 7th March 2021]

[viii] Unpublished Excavations ( [Assessed 7th March 2021]

[ix] Do it Yourself Lake Dwellings ( [Assessed 7th March 2021]

[x] Crannog Material ( [Assessed 7th March 2021]

[xi] Relics of the Past (( [Assessed 6th March 2021]

[xii] Mayo Archaeology ( [Assessed 6th March 2021]

[xiii] County Mayo ( [Assessed 6th March 2021]

[xiv] Possible Crannóg ( [Assessed 7th March 2021]

[xv] Crannógs ( [Assessed 7th March 2021]

[xvi] Looking at Crannógs (( [Assessed 7th March 2021]

[xvii] Crannogs ( [Assessed 7th March 2021]

[xviii] Mc Mahon of Monaghen ( [Assessed 7th March 2021]

[xix] Crannógs ( [Assessed 7th March 2021]

[xx] Crannógs ( [Assessed 6th March 2021]

[xxi] Artificial Islands ( [Assessed 7th March 2021]


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