Big stones, and three Breton words
Megalith comes from the Greek megas, great, and lithos, stone, and it means exactly that: a large stone set up on purpose. Two of the main types take their names from Breton, the Celtic language of Brittany, where these monuments are everywhere. A menhir is maen hir, a “long stone”. A dolmen is usually explained as taol men, a “stone table”, which is what a dolmen looks like once the earth that covered it has gone.
A megalith is more than the stone. Look at the socket it stands in, the small packing stones that wedge it, the ditch or bank around it, and the mound that may have covered it before the plough took it away. All of that is part of the monument.
Menhirs: one stone, or three thousand
A single menhir can mark a place: a ridge, a ford, a crossing of paths. Set many in rows and you get an alignment. At Carnac, in Brittany, about 3,000 stones stand in lines over some 4 km. The Ménec group alone has 1,099 stones in 11 rows stretching for 1,167 m. Most were set up between about 4800 and 3500 BCE, and since July 2025 the megaliths of Carnac and the Morbihan coast have been a UNESCO World Heritage Site.
A few kilometres away, at Locmariaquer, lies the record holder. The Grand Menhir Brisé, the “great broken menhir”, was a single block of granite about 20 m long, weighing somewhere between 280 and 330 tonnes depending on whose estimate you read. It was raised around 4500 BCE and now lies on the ground in four pieces. How it fell is still argued over.
Can you date a stone? Not directly. Archaeologists date charcoal or bone in the socket or in pits nearby, which is why megalith dates always come as ranges.
Dolmens and passage graves
A dolmen is a chamber of stone, two or more uprights carrying a capstone. Most were once buried under a mound of earth or stones, so that only the entrance showed; the bare “stone tables” you see today are skeletons that have lost their skin. A passage grave adds a narrow corridor leading to the chamber, all sealed under the mound.
Inside, archaeologists find human bones, often moved and mixed by later burials, along with pottery and tools. These chambers were reopened and enlarged for centuries. Entrances face a chosen direction, and Newgrange, in Ireland, built around 3200 BCE, makes the point unforgettable: a small opening above the door, the roof-box, lets the rising sun shine down the passage into the chamber for about 17 minutes around the winter solstice. Its kerbstones are carved with spirals, lozenges and zigzags.
Stone circles
A stone circle is a ring of uprights, an open-air room with gaps that work as entrances. Some line up with the solstice sunrise or sunset. Stonehenge, the most famous, grew in stages: a round ditch and bank around 3000 BCE; the central stones around 2500 BCE, with big sarsens from about 25 km away and bluestones from the Preseli Hills in Wales; lintels fixed with mortise and tenon joints, as if the stones were timber. In 2024 a study traced the six-tonne Altar Stone to north-east Scotland, about 750 km away.
How do you move a 300-tonne stone?
Slowly, and with a lot of people. Quarry marks show blocks split from bedrock with wedges. Sledges and rollers moved them over prepared tracks; on slopes, teams built earth ramps. To stand a stone up, they levered one end a little at a time onto stacks of timber, then let it slide into a socket lined with packing stones. Lintels went up the same way, or were walked up a ramp of planks and earth.
Experiments with volunteers, timber and rope have moved stones of many tonnes like this. The numbers change with the stone and the ground; the method doesn’t. Leaning stones and shifted lintels in the record show that mistakes and second attempts were part of the job, and the Grand Menhir Brisé may be the biggest of them.
What were they for?
Several things, and not everywhere the same. Many dolmens held human remains, so burial is real. Many circles line up with the seasons, so marking the year is real too, although none of them works as a clock. Fields of menhirs needed organisation, which suggests leadership, feasting or both. And many monuments sit where routes, rivers and ridges meet, often within sight of each other. On some stones you can still find cupmarks, small round hollows pecked into the surface.
The same taste for huge stone and controlled entrances carried on into the Bronze Age, most spectacularly in Sardinia’s nuraghi.
Where to see them
Carnac’s alignments can be seen from paths around the fields, with closer access in winter or on guided visits; Locmariaquer’s broken menhir is a short drive away. Newgrange is visited through the Brú na Bóinne visitor centre, and Stonehenge from the visitor centre near Amesbury. Access rules change by season, so check the official websites before you go.
Sources
- UNESCO World Heritage Centre, “Megaliths of Carnac and of the shores of Morbihan” (2025); Centre des Monuments Nationaux, “Alignements de Carnac” and “Site des mégalithes de Locmariaquer”.
- National Museum of Ireland, “The Winter Solstice at Newgrange”.
- English Heritage, “Building Stonehenge”; UNESCO World Heritage Centre, “Stonehenge, Avebury and Associated Sites”.
- A. J. I. Clarke et al., “A Scottish provenance for the Altar Stone of Stonehenge”, Nature 632 (2024).
- Historic England, “Introductions to Heritage Assets: Stone Circles”.
- Oxford Radiocarbon Accelerator Unit, “Radiocarbon Dating: An Introduction”.
