At the bottom of the Atlantic off the western coast of France, researchers uncovered an unusual stone structure that offered a new perspective on the lives of ancient coastal communities. Beneath the water lay a straight line of granite blocks spanning approximately 120 meters. The wall rests at a depth of about nine meters and only becomes visible during periods of rare underwater clarity. Analysis indicated it was built over seven thousand years ago, long before the appearance of early megaliths such as Stonehenge.
The construction comprises massive stones set in pairs and reinforced with smaller slabs. The total weight of the monoliths reaches several thousand tons, making the edifice the largest underwater finding in France. Scientists suggest the wall might have served as coastal reinforcement, which shifted due to rising sea levels after the Ice Age. Another theory describes it as a fish trap, where tides guided prey between the stone elements.
Near TAF1, other smaller stone lines have also been found. These form a network resembling a planned landscape. Such constructions suggest the ancient inhabitants’ desire for a more settled existence, even though agriculture was not yet the main occupation. Creating these lines demanded material knowledge, the skill to transport heavy stones, and collaborative work, pointing to a developed social organization.
The discovery resonates with local folklore. The isle of Sein is known for the legend of the city of Ys, which, according to tradition, perished due to a flood. Researchers speculate that the myth might stem from real events related to sea-level rise and the submergence of coastal settlements. The island’s history is also full of other tales—from accounts of priestesses with mystical powers to numerous shipwrecks that cemented Sein’s somber reputation. Later, it became known partly for its residents’ involvement in the “Free France” movement during World War II.
Scientists emphasize that the TAF1 discovery helps us reimagine the map of Europe in deep antiquity. The rising sea may have concealed many early settlements beneath the waves, and a significant portion of human history still remains hidden on the seabed.
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