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Origin and history

The Dolmen des Trois Pierres, also known as the Dolmen du Prieuré or Bois-Savary, is a megalithic building located in downtown Saint-Nazaire, on the Dolmen Square. It consists of three gneiss slabs forming a trilith, with a blanket table of 3.45 m long, and a 4 m high granulite menhir, straightened in 1928. Originally, the site belonged to Saint-Jean-Baptiste Priory of Saint-Nazaire, which explains its historical name as dolmen of the Priory. The first written records date back to 1679, in a seigneurial declaration evoking high stones on the island of Bois-Savary.

In the 19th century, the dolmen was described as a remarkable trilith, surrounded by remains of a possible covered driveway. The old drawings, like those of Bachelot de la Pylaie (1848), confirm its present disposition, although destruction and urban development have altered its environment. The menhir, initially lying behind the dolmen, was raised by Marcel Baudouin in 1928, who also noted the presence of cupules on his eastern face. Four other blocks, including one presumed lects, were identified during excavations, but only two remain today.

Ranked a historic monument in 1889, the dolmen is a rare example of an authentic urban megalith, preserved in the middle of a square. Its authenticity, sometimes contested because of the changes it has undergone, is defended by archaeologists such as Jean L-Helgouach, who emphasize the consistency of the old descriptions. The site also includes traces of a extinct tumulus, reinforcing the hypothesis of an ancient covered alley, typical of Armomeric megalithism.

The current location, 400 m from the port and 1 km from the station, results from the extension of Saint-Nazaire in the 19th century. The dolmen and the menhir, although redesigned, remain major witnesses of local prehistory. Their preservation in the city centre makes it a unique case in France, illustrating the adaptation of archaeological remains to modern urbanization.

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