A tiny village in France is calling on the help of the public to uncover the meaning behind a mysterious 230-year-old rock inscription.
The unknown message – which includes 20 lines of text written using both French and Scandinavian characters – was discovered on rocks hidden inside a cave on the outskirts of Plougastel-Daoulas, France.
Since making the discovery almost five years ago, experts have made various attempts to decipher the inscription which reads: 'ROC AR B... DRE AR GRIO SE EVELOH AR VIRIONES BAOAVEL... R I OBBIIE: BRISBVILAR... FROIK...AL'.
However, Mayor of Plougastel-Daoulas Dominique Cap said locals are no closer to uncovering the language of the secret code, which is believed to be written in a now-extinct language that was spoken in Northern France between the 9th and the 11th century AD.
'There are people who tell us that it's Basque and others who say it's Old Breton,' he told AFP.
The rock also features the image of a sail ship, a sacred heart and the dates '1786' and '1787'.
There have been suggestions the markings relate to establishments of fortifications near the cove in which the rock was found.
Adding to the mystery, the one-metre high rock is submerged by water, only visible when the tide is out.
Local linguists, academics, and epigraphers experts familiar with Breton history and culture have been baffled by the words and symbols, so the town has opened the puzzle to the public.
People now have until November 30 to submit their answers, with a jury to decide which interpretation is most likely.
'We've asked historians and archaeologists from around here, but no-one has been able to work out the story behind the rock. So we thought maybe out there in the world there are people who've got the kind of expert knowledge that we need,' he said.
'Rather than stay in ignorance, we said: ‘let's launch a competition','
The winner will be awarded $A3200.