A stone slab from the Bronze Age is believed to be the oldest 3D map in Europe, researchers say.
The Saint-Bélec slab was first unearthed in Brittany in 1900 but spent the last century in the cellars of the Musée d'Archeologie Nationale in Saint Germain en Laye, west of Paris.
It is believed to date back to the early Bronze Age, which started about 3,100 BC.
It was "rediscovered" in 2014 by researchers Yvan Pailler and Clément Nicolas who hunted it down after reading about it in an old article.
Together, they analysed the markings and engravings on the slab which is 2.2 metres long and 1.53 metres wide.
They concluded that it must be a map because some of the markings are repeated and linked together by lines to create a network and several are more deeply engraved as if to highlight and mark their importance.
This would make it Europe's oldest known 3D map.
They then "georeferenced" the engravings to see whether they matched the area close to where it was first unearthed and found that they correspond to a zone of approximately 30 km long following the course of the Odet river.
The slab has yet to yield all of its secrets. Researchers are still bemused as to why it was found in a tomb. One of their hypotheses is that the tomb was built for the last representative of an important lineage of princes who reigned over the territory then or for a scribe, the author of the map who would also have been buried, as per tradition, in a tumulus.