• The slab of Saint-Bélec was discovered in 1900 in a Breton tumulus from the Early Bronze Age, according to our partner The Conversation.

  • This nearly one-ton stone is covered with engravings made of repeated patterns (circles, squares, cups) joined by lines, which makes it look like a map.

  • The analysis of this discovery was carried out by Yvan Pailler, archaeologist in charge of operations at the National Institute for Preventive Archaeological Research (INRAP) and Clément Nicolas, Marie Curie postdoctoral fellow at the University of Bournemouth (United Kingdom).

“Describing this curious monument with its cups, circles and various engraved figures, in which some see a shapeless human representation and that of an animal, is difficult.

[…] Let us not be led astray by fantasy, leaving it to a Champollion, who will perhaps find himself one day, to read it to us.


Paul du Chatellier thus summarized the questions about the engravings on the slab of Saint-Bélec that he had just unearthed in a tumulus from the Early Bronze Age (2200-1600 BC) in Leuhan in the west of Brittany.

He then had it transported to his residence and private museum, the manor of Kernuz in Pont-L'Abbé (Finistère).

After his death, his important archaeological collection was acquired in 1924 by the National Archeology Museum installed in the castle of Saint-Germain-en-Laye.

The memory of this slab fading over time, it will only recently be found in one of the cellars of the museum's castle.

A representation of fields?

In 1994, Jacques Briard, researcher at the CNRS and specialist in the Bronze Age, wondered about the interpretation to be given to the slab of Saint-Bélec, for which he only had the drawing and the photo published by P. du Chatellier.

He thinks he sees the representation of a system of fields associated with cupules (points engraved in the rock), like what we know in the Vallée des Merveilles (Mercantour) or in the Val Camonica (North of Italy).

The photograph of Paul du Chatellier on which Jacques Briard was based for his study © Departmental Archives of Finistère (via The Conversation)

Years later, we will share this feeling: the engravings of this stone, made of repeated patterns (circles, squares, cups) joined by lines, resemble a map.

However, it is impossible to go further without being able to study this large slab of shale measuring 2.20 m in length and 1.50 m in width for a weight approaching a ton.

A sleeping beauty

There was no assurance that the slab of Saint-Bélec had reached Saint-Germain-en-Laye and no mention made of it, it was believed until recently.

In the 1990s, Renan Pollès, amateur filmmaker and archaeologist, investigated another ornate stone from the Chatellier collection, the Renongar slab (Plovan), which he then published in the

Revue archeologique de l'Ouest


Château de Saint-Germain-en-Laye © EXistenZ / Wikimedia CC BY-SA 3.0

He finds it in a niche in the moat of the castle of Saint-Germain-en-Laye and mentions in his publication two other engraved stones from the same collection, that of the Minven chest in Tréogat and a second which he thinks comes from the passage tombs of Butten er Hah on the island of Groix, excavated in the years 1890-1900 by Louis Le Pontois, naval commander and conscientious archaeologist. However, this one, to protect the engraved stones of Butten er Hah, buried them on the spot. This blunder was made up for by a curator, correcting the copy of the article by Pollès kept in the library of the National Archeology Museum and mentioning in passing that it was the slab of Saint-Bélec.

This simple note indicated that the slab must have been in Saint-Germain-en-Laye, but where?

With the help of the curator at the time, we surveyed all the places where it could have been stored.

A single niche in the moat no longer contained such a slate slab and it was not in the museum's lapidary collections either.

It is thanks to the memory of a museum keeper that we ended up finding it in 2014 in one of the cellars, where it had been moved to protect it from bad weather.

We were not at the end of our troubles, because the slab was stored singly on a wooden structure against a wall which prevented access to the engravings.

After having succeeded in collecting some subsidies, a specialized team was finally able, in 2017, to lay the slab flat so that we could finally study it.

Found in this cellar of the National Archeology Museum, the slab was stored with the face engraved against a wall.

Meeting it required complex logistics © Clément Nicolas / Bournemouth University & Yvan Pailler / UBO-Inrap (via The Conversation)

A relief map

When confronted with the Saint-Bélec slab, several observations confirmed our cartographic interpretation.

First observation: we are missing pieces of the puzzle.

In the tomb, the slab was broken in its upper third but the excavator had recovered a good part of the fragments and had restored them in 1900. We subsequently found one of these fragments in the museum's reserves.

Second observation, the photograph of Paul du Chatellier was not misleading and its drawing fairly faithful, allowing the missing pieces to be stitched together.

Finally, a whole part of the slab has been carved into a hollow to form a triangle, in which a square motif in bas-relief has been made and a branched line staked.

The whole evoked a valley and the confrontation with the topography around the tumulus of Saint-Bélec would quickly become obvious.

This overlooks the upper Odet valley, which has a similar angulation and which is closed to the west by a granite tabular massif, which is exactly the panorama that can be seen from the Saint-Bélec tumulus.

We were dealing here with the relief of a portion of the Odet valley over about fifteen kilometers.

Topography of the surroundings of the Saint-Bélec tumulus transferred to the slab © authors - according to IGN (via The Conversation)

However, our certainties were not enough to make a demonstration to convince the community of archaeologists;

especially since some, in a resolutely evolutionary conception, still doubt that Man could have drawn up maps before the advent of cities, the State and writing ...

A dive into the ethnographic literature shows that preindustrial societies have no difficulty in figuring out maps (moreover, without a mental map, it is not possible to find one's way in space) and that some of them were carving maps in stone not so long ago in South Africa or Australia.

It is only by exchanging with fellow geographers, Pierre Stéphan and Julie Pierson, that we succeeded in strengthening our demonstration.

They pushed us to develop our hypotheses to better test them from a statistical point of view.

This is how the arrangement of other lines, which formed ramifications and meanders, appeared to us as the representation of other rivers around.

Spatial analyzes have been used to quantify what the human eye has so far seen but could not demonstrate.

They make it possible to statistically compare shapes (Pompeiu-Hausdorff distance, Wilcoxon test) or networks (Jaccard distance, Mantel test), here the engravings and the topographical elements supposedly represented.

Detail of the engraved slab depicting the Odet valley © V. Lacombe / DigiScan3D and P. Stéphan / CNRS (via The Conversation)

Thus, we were able to assess the degree of similarity between the network of lines engraved on the slab and the existing hydrographic network.

The convincing results (around 70-80%) were found to be equivalent to those obtained for mental maps collected from the Tuaregs of Niger and the Papuans in New Guinea.

Map of a Bronze Age territory

Although several topographical features have been identified - the Odet valley, the Black Mountains, the courses of the Aulne, the Isole and the Stêr Laër - there are a number of patterns that we have not yet managed to decode.


The freshness of the engravings suggests that a relatively short time elapsed between the engravings and the use of the slab as the wall of an Early Bronze Age tomb.

And several patterns could correspond to structures from this period, such as tumuli (cupules), enclosures (circular patterns, potatoids) or fields (reticulate patterns).

To test the predictive potential of this engraved map and to perfect its demonstration, it would now be necessary to succeed in locating and dating some of the sites that could be shown there.

What to occupy us the next years in this sector of the Black Mountains.


Ancient sexual representations shed light on the civilizations that produced them


Archeology: From amputation to prosthesis, how our ancestors "repaired" their handicapped people

This analysis was written by Yvan Pailler, archaeologist in charge of operations at the National Institute for Preventive Archaeological Research (INRAP) and Clément Nicolas, Marie Curie postdoctoral fellow at the University of Bournemouth (United Kingdom).

The original article was published on The Conversation website.

Declaration of interests

Yvan Pailler does not work, does not advise, does not own shares, does not receive funds from an organization that could benefit from this article, and has not declared any affiliation other than his research organization.

Clément Nicolas received funding from the University of Paris 1 Panthéon-Sorbonne, Ministry of Culture, Departmental Council of Finistère, Fyssen Foundation, European Commission

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