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Origin and history

The cairn of Carn Island, located in the commune of Ploudalmezeau in Finistère, is a remarkable megalithic ensemble of Neolithic. It consists of a trapezoidal primary cairn, built around 4200 BC, containing three dolmens aligned with corridor and corbelling vault. This cairn was covered in the final Neolithic by a circular "massive ban", without entry, constituting a unique example of architectural transformation.

The excavations carried out between 1954 and 1972 by Pierre-Roland Giot revealed that the central dolmen, dated by carbon 14 in 1959, is 1,600 years older than the oldest Egyptian pyramid, upsetting knowledge of European megalithism. The southern and central dolmens, built around 4200 B.C., preceded by centuries the northern dolmens (c. 3600 B.C.), whose chamber divided into two subspaces bears witness to an architectural evolution.

During World War II, the Germans partially destroyed the cairn to install a casemate, damaging the southern dolmen. Ranked a Historic Monument in 1955, the site was restored between 1967 and 1972, including the reconstruction of the vaults and the consolidation of the walls. Today, the secondary cairn, of circular shape, dominates Carn Island, accessible at low tide by a road of rocks.

The furniture discovered (shale pearls, pottery, flint tools) suggests a funeral and ritual use over more than a millennium. The more recent north dolmen delivers a separate furniture, dating from about 3000 B.C., indicating a late reappropriation of the site. The alignment of the dolmens to the rising sun of the winter solstice and their sophisticated architecture underline their symbolic and astronomical role.

The island Carn, a coastal island of the Celtic Sea, was originally a continental site overlooking the sea of 20 meters during the Middle Neolithic, before the rise of the waters. The primary cairn, initially visible and imposing, was deliberately buried under the circular cairn, perhaps to mark a cultural or religious rupture. This "massive ban" remains an archaeological mystery, without equivalent known in Europe.

Owned by the Finistère department, the Carn island cairn illustrates the ingenuity of Neolithic builders and their mastery of dry stone construction techniques. Giot's work saved this unique heritage, while posing persistent questions about funeral practices and beliefs in prehistoric Breton societies.

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