What’s the Difference Between a Dolmen, a Cairn, and a Tumulus?

Imagine, if you will, that you are among the first speakers of a proto-Gaelic or proto-Goidelic language aboard one of the first Celtic ships to reach Ireland.

The Emerald Isle doesn’t look exactly like it does today. There are no cities, of course. And there are definitely more trees. 

But some significant features remain the same. Namely, in addition to the abundance of bogland and rolling green hills, there are many impressive megalithic structures and other human-made monuments dotting the Irish landscape.

But wait, that means…

Correct: You are not alone on this island.

Because while you may be among the first speakers of a Celtic language to reach Ireland, people have already been living here for thousands of years. 

People who built hundreds of dolmens, cairns, and tumuli.

These Stone Age structures will soon feature into the stories you and your fellow Gaels tell around the fire. They will become the royal abodes and final resting places of your gods and heroes, and, in some cases, portals to many a wondrous Celtic Otherworld.

Indeed, without these dolmens, cairns, and tumuli, Irish mythology would be a very different storytelling tradition from what it is today.

Which begs the question. Or questions, rather:

What is a dolmen? What is a cairn? And what is a tumulus? 

Are they the same thing?

The short answer: No.

The longer answer: in some cases they are the same thing, sort of. Or at least they can be part of the same structure. We’ll get into it.

But first, let’s lay the groundwork (sorry) with some simple definitions.

FYI: You can watch a video adaptation of this post right here. (Text continues below.)

The Definition of Dolmen

A dolmen is a stone monument consisting of a large flat capstone lying across two or more vertical stones. Often referred to as a “portal tomb” on account of the opening or portal left between the vertical stones, the dolmen is also sometimes called an “altar tomb” or, occasionally, a “cromlech,” although a cromlech can also mean a stone circle (which is a subject for another article/video).

Dolmens are found the world over but some of the oldest were built in what is now Brittany perhaps as far back as 5,000 BCE. They started cropping up in Ireland, Britain, and Scandinavia in 4,000 BCE. And for context, academic consensus places the emergence of Proto-Celtic, the precursor to all Celtic languages, at around 1,300 BCE. 

Granted, adherents of Barry Cunliffe’s and John T. Koch’s “Celtic From the West” theory would place the development of Proto-Celtic further back at around 3,000 BCE, but assuming such a timeline still wouldn’t change the fact that the oldest dolmens we find in what we now think of as the Celtic World couldn’t have been built by Celtic-speakers because Celtic-speakers didn’t exist yet.

Moving on.

The Definition of Cairn

A cairn is a pile of rocks.

That was an easy one. 

Okay, fine. A cairn is a mound or stack of stones that is raised as a landmark or memorial.

In prehistoric Ireland and Scotland, a specific type of cairn, known as a court cairn or court tomb, was incredibly popular, with approximately 400 being built in the former and approximately 100 being built in the latter between the years of 3,900 and 3,500 B.C.E.

And while it can take on a variety of configurations, the court cairn is typified by the presence of an uncovered courtyard—often circular or oval-shaped—that is connected to one or more roofed chambers.

The Definition of Tumulus

Finally, a tumulus (plural: tumuli) is an artificial earthen mound, especially one that is raised over a grave or graves.

Also known as a barrow or, simply, a burial mound, a tumulus can sometimes feature an internal chamber as well as a long corridor or passage leading to said chamber, in which case the structure can also be classified as a passage tomb or passage grave.

Ireland’s largest and most famous passage tomb/tumulus is the Newgrange monument. Built around 3,200 BCE, it measures nearly 280-feet (or 85-meters) across at its widest point.

However, the title of largest tumulus in Europe goes to the Saint-Michel tumulus in Brittany. Built between 5,000 and 4,000 BCE, the oval-shaped monument measures approximately 410-feet (or 125-meters) long by 190-feet (or 58-meters) wide.

How Dolmens, Cairns, and Tumuli Are Related

Now, at first glance, these three structures—dolmens, cairns, and tumuli—may seem, at least architecturally speaking, entirely unrelated. 

Until you consider the following:

If you take a dolmen, and cover it with a bunch of stones, what do you get? 

The answer: a cairn…with a chamber in the middle. 

Similarly, if you take a dolmen and fill it in with a bunch of earth, what do you get?

The answer: a tumulus…with a chamber in the middle.

Indeed, archaeologists have theorized that many of the dolmens we see scattered around Ireland and Brittany and elsewhere today are actually the remnants of ancient cairns and tumuli whose stones and earth, respectively, have been hauled away for other uses. 

What’s more, when archaeologists explore the chambers of existing cairns and tumuli, they often find dolmens serving as the frames or support systems that make those aforementioned structures possible. 

Sooo yeah. Dolmens, cairns, and tumuli are different. But sometimes the former are essential components of the latter. 

Then there’s the whole ritual significance of these structures, something we’ve barely touched on. 

So let’s crawl in, shall we?

Dolmen Origins and Mythology

And let’s start with the original purpose of dolmens, and more specifically, let’s dispel a common myth about them, which arose on account of their table-like appearance. That myth? That dolmens were altars upon which druidic sacrifices were made. 

Here, I’ll let Scottish scholar J. A. MacCulloch do the mythbusting for this one.

“The old idea that dolmens were Celtic altars is now abandoned. They were places of sepulture of the Neolithic or early Bronze Age, and were originally covered with a mound of earth. During the era of Celtic paganism they were therefore hidden from sight.”

(source: The Religion of the Ancient Celts)

To recap: dolmens weren’t altars, they were burial sites. And, as we’d already established, they weren’t Celtic, they were Neolithic, meaning they were constructed in the New Stone Age.

For a deeper understanding of who built these dolmens, and cairns, and tumuli, as well as why they were built, let us turn to the Welsh scholar Edward Anwyl:

“In death, [neolithic man] was buried with his kin in long mounds of earth called barrows, in chambered cairns and cromlechs or dolmens. The latter usually consist of three standing stones covered by a cap-stone; forming the stony skeleton of a grave that has been exposed to view after the mound of earth that covered it has been washed away. In their graves the dead were buried in a crouching attitude, and fresh burials were made as occasion required. Sometimes the cromlech is double, and occasionally there is a hole in one of the stones, the significance of which is unknown, unless it may have been for the ingress and egress of souls.”

(source: Celtic Religion in Pre-Christian Times)

After the Celts showed up on the scene, of course, the raison d’être of these structures would be reimagined. 

For example, the holed stones, thought to facilitate soul transportation after death, became associated instead with life and healing. To quote MacCulloch:

“Holed dolmens or naturally pierced blocks are used for the magical cure of sickness both in Brittany and Cornwall, the patient being passed through the hole. Similar rites are used with trees, a slit being often made in the trunk of a sapling, and a sickly child passed through it… In these rites the spirit in stone or tree was supposed to assist the process of healing, or the disease was transferred to them, or…there was the idea of a new birth with consequent renewed life, the act imitating the process of birth. These rites are not confined to Celtic regions, but belong to that universal use of magic in which the Celts freely participated.”

In Ireland, meanwhile, dolmens would take on a more, shall we say, specifically Celtic meaning—one tied to a specific myth: The Pursuit of Diarmuid and Gráinne. 

Belonging to the Fenian Cycle of Irish mythology, the tale sees a warrior of the Fianna, Diarmuid Ua Duibhne a.k.a. Diarmuid of the Love Spot, foster-son of the love-god Aengus Óg, run off with the princess Gráinne, daughter of the Irish high-king Cormac mac Airt.

The only problem? 

Gráinne is betrothed to the leader of the Fianna, the Irish hero Fionn mac Cumhaill. So, Diarmuid and Gráinne get chased all over Ireland, and naturally, the dolmens that can be found all over Ireland become known as “Diarmaid and Grainne’s beds.” These are the places where the eloping fugitive lovers allegedly slept—presumably very uncomfortably. 

Although maybe they didn’t do much sleeping. (Wink.)

And given this romantic connotation, Irish dolmens become associated with fertility, and women who are keen on having children pay visit to these so-called “beds.”

Granted, the 16th-century-born Irish historian Geoffrey Keating argued that before Irish dolmens became associated with Grainne, they were associated with a different mythological figure, the Irish sun-goddess Grian. Grian being the Irish word for sun.

But I digress.

Back in Brittany, dolmens would become the abodes of a race of fairy-like beings known as korrigans (also: corrigans), which, according to American anthropologist Walter Evans-Wentz, were “little beings not more than two feet high, and beautifully proportioned, with bodies as aerial and transparent as those of wasps,” (source: The Fairy-Faith in Celtic Countries).

In the Channel Islands, meanwhile, dolmens were traditionally thought of as the “general rendezvous of our insular sorcerers,” to quote British folklorist Edith F. Carey, who went on to note that manuscripts from the sixteenth and seventeenth centuries described the structures as “altars of the gods of the sea,” (source: The Channel Islands).

Given these pagan associations, it is perhaps not surprising that when Christians arrived on the scene, dolmens occasionally fell under their holy hammers. At least according to legend.

For example, a Welsh legend tells us that the 6th-century Christian bishop Saint David split the capstone of the Maen Ketti dolmen a.k.a. the Maen Ketti cromlech, in order to prove to the locals that there was nothing divine about it. That destroyed dolmen is still around, by the way, only it is more commonly known today as Arthur’s Stone—as in King Arthur.

And just to clarify, I’m referring to the Arthur’s Stone on the Gower Peninsula in Wales because it turns out there is another Arthur’s Stone in Herefordshire, England, which also happens to be a Neolithic dolmen. 

These things are everywhere.

Now, let’s move on to cairns. 

Cairn Origins and Mythology

Let me begin by offering you the following warning, courtesy of Evans-Wentz:

“A heap of stones in a field should not be disturbed…The fairies are said to live inside the pile, and to move the stones would be most unfortunate. If a house happens to be built on a fairy preserve, or in a fairy track, the occupants will have no luck. Everything will go wrong. Their animals will die, their children fall sick, and no end of trouble will come on them.”

For a modern, horror-filled take on what kind of trouble you can expect if you mess with a cairn, look no further than the Irish film Boys from County Hell, featured in my video/article on the top 10 Irish horror films. Some light spoilers ahead—consider this your second warning—the film is based on the legend of Abhartach, the infamous Irish vampire or neamh-mairbh (“walking dead”) who can only be subdued by way of stabbing with a sword made of yew wood followed by an upside-down burial. 

However, while in the film a cairn is built over top of the buried Abhartach in order to contain him, in the legend it’s a slab of rock. And to this very day you can see this Irish vampire’s alleged grave marker in County Derry—it’s called the Slaghtaverty Dolmen.

Yes, another dolmen.

Back to the cairns.

There is a long tradition of cairns being associated with ghostly or otherwise supernatural beings, a tradition that extends to the modern era. Hence, writing in 1911, MacCulloch noted:

“In Celtic districts a cairn or a cross is placed over the spot where a violent or accidental death has occurred, the purpose being to appease the ghost, and a stone is often added to the cairn by all passers-by.”

Moving backward in time, Irish kings were often inaugurated on ancestral burial cairns, and these same cairns were said to have provided prophetic visions to those who slept on top of them.

For example, legend has it that the lost story of the Táin Bó Cúailnge (or Cattle Raid of Cooley) perhaps the most famous epic in all of Irish mythology, was recovered by two bards who slept atop the burial cairn of Fergus mac Róich, an exiled king of Ulster of who features prominently in the tale.

For the record, the Táin is part of the Ulster cycle of Irish mythology, but we find references to cairns in all four cycles.

For example, during the Fenian Cycle, when Fionn mac Cumhaill’s grandson Oscar is killed in battle, Oscar’s widow Aidin dies shortly thereafter from grief. Oscar’s father Oisín, the son of Fionn mac Cumhaill, buries Aidin on the Ben of Howth (known in Irish as the Beann Éadair) and raises a great cairn over her grave.

But by far it is the Mythological cycle where we encounter the most references to cairns. 

There’s the cairn of Fiachu, for example, upon which the exiled Lugaid mac Tail lights a druidic fire, out of which bursts five streams of flame. This feat earns Lugaid a new name: Delbaeth, meaning shape-fire, or perhaps fire-shaped.

But perhaps the most famous mythological cairn is the one that gets created during the second battle of Mag Tuired, which sees the Tuatha Dé Danann, the “good” Irish gods, if you will, facing off against the monstrous, marauding Fomorians led by Balor of the Evil Eye.

During the battle, the Fomorian warrior Octriallach discovers that Dian Cecht, the Irish god of medicine, keeps bringing his slain Tuatha Dé Danann compatriots back to life by dunking them in the Tipra Slaine (or Spring of Life). 

So Octriallach rallies some of his fellow Fomorians to dump a bunch of stones in the spring, filling it in and, in the process, creating the Cairn of Octriallach. Spoiler alert: the Fomorians still lose.

Jump ahead to the Kings Cycle a.k.a. Historical Cycle of Irish Mythology, and the cairn will be reimagined as the burial site of Ailill mac Echach Mugmedóin, half-brother of the Irish High King, Niall of the Nine Hostages.

And jump over from the realm of myth and legend to the realm of archaeology, and the Cairn of Octriallach is now more commonly known as the Heapstown Cairn. Located in County Sligo, the structure dates back to around 3,000 BCE, and while today it stands between 20 and 30 feet (or 6 and 10 meters) high, illustrations from the 1800s show that it was originally much taller and had a standing stone on its summit.

But infrastructure wasn’t the only threat to the survival of ancient cairns. As was the case with dolmens, Christians were allegedly intimidated by the reverence these monuments commanded. Hence, in a prayer attributed to Saint Columba, the Irish Abbot asks God to dispel “this host (i.e., the pagan gods) around the cairns that reigneth.”

Apparently, a lot of the stones got carted away to build roads, which is a story with an interesting parallel to the one we explored in my video/article on Celtic sacred trees, wherein an Irish fairy bush was in danger of being demolished to make way for a new motorway.

Speaking of gods attaching themselves to ancient monuments, it’s time to talk about tumuli. 

Tumulus Origins and Mythology

As mentioned, these massive, human-made hills likely originated as burial mounds. And that function is represented in the Irish myths.

For example, after being slain by Balor of the Evil Eye during the second battle of Mag Tuired, Nuada Airgetlám (Nuada of the silver arm or hand), the first king of the Tuatha Dé Danann, is interred beneath a tumulus: the Grianan of Aileach. Today, there is a stone ringfort on that site, a structure that was built by Celts (re: the Gaels), probably during the sixth or seventh century CE, but the adjacent tumulus is undoubtedly much older. 

And it was the presence of that tumulus that likely drew the Gaels to that site in the first place. As MacCulloch noted:

“Certain passages in Irish texts also describe burials, and tell how the dead were interred with ornaments and weapons, while it was a common custom to bury the dead warrior in his armour, fully armed, and facing the region whence enemies might be expected. Thus he was a perpetual menace to them and prevented their attack. Possibly this belief may account for the elevated position of many tumuli.”

Underlying this belief (pun absolutely intended) was the Celtic concept of the immortal soul. To the ancient Celts, death in this world meant life in one of the Otherworlds. Or as MacCulloch put it:

“If the Celts cherished so firmly the belief that the dead lived on in the grave, a belief in an underworld of the dead was bound in course of time to have been evolved as part of their creed. To it all graves and tumuli would give access.”

FYI: You can learn more about how the ancient Celts thought about death and the afterlife and the transmigration of souls in my video/article on Celtic Otherworlds.

But for now, let us return to the land of the living. 

Because in Irish mythology, tumuli are more closely associated with living gods—specifically members of the Tuatha Dé Danann who are driven underground following the Milesian invasion.

A quick recap: The Milesians are the last of six mythical races to settle in Ireland and are thought to represent the arrival of Celtic culture. They defeat the Tuatha Dé Danann, and thus the gods are forced to retreat to their subterranean palaces, i.e. their sídhe—one of the most notable of which is the Brú na Bóinne, or Palace of the Boyne, site of the aforementioned Newgrange Monument. 

To gain a more thorough understanding of the site’s importance, let’s listen to a poem recorded in the 14th-century Book of Ballymote and the dedication that precedes it: 

‘Ye Poets of Bregia, of truth, not false,’ the wonders of the Palace of the Boyne, the Hall of the great god Daghda, supreme king and oracle of the Tuatha de Danann, are thus celebrated:—

Behold the Sidh before your eyes,

It is manifest to you that it is a king’s mansion,

Which was built by the firm Daghda;

It was a wonder, a court, an admirable hill.

In this context, the tumulus at Newgrange is less a tomb and more a home. And interestingly, in the myths, the Dagda, the father of the Irish gods, doesn’t even get to live there permanently, as his son Aengus Óg tricks him out of it.

See, after the whole Milesian incident, the Dagda wants Brú na Bóinne for himself, because it’s so awesome, but Aengus Óg says, “hey dad, come on, let me just stay here for a day and a night,” and the Dagda agrees to this, but it turns out what Aengus had actually said was “let me stay here day and night,” as in forever. Et voila.

Ultimately, the Tuatha Dé Danann would shrink in the popular imagination, both literally and figuratively, until they became the aes sídhe, or people of the hills, otherwise known as fairies. 

Hence, as Evans-Wentz noted: 

“Throughout Ireland there are many ancient, often prehistoric, earthworks or tumuli, which are popularly called forts, raths, or dúns, and in folk-belief these are considered fairy hills or the abodes of various orders of fairies. In this belief we see at work a definite anthropomorphism which attributes dwellings here on earth to an invisible spirit-race, as though this race were actually the spirits of the ancient Irish who built the forts.”

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Want to learn about the darker side of Irish and Celtic mythology? Check out…

Samhain in Your Pocket

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Irish Monsters in Your Pocket

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Neon Druid: An Anthology of Urban Celtic Fantasy

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More the listenin’ type?

I recommend the audiobook Celtic Mythology: Tales of Gods, Goddesses, and Heroes by Philip Freeman (narrated by Gerard Doyle). Use my link to get 3 free months of Audible Premium Plus and you can listen to the full 7.5-hour audiobook for free.