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Origin and history

Dissignac is a megalithic funeral monument located in Saint-Nazaire, Loire-Atlantique. Dated between 4700 and 4500 B.C.E., it is considered the oldest megalithic building in the department. Contemporary to the broken Great Menhir of Locmariaquer (Morbihan), it precedes by 2000 years the pyramid of Djéser in Egypt. Ranked a historic monument in 1889, it is only accessible in July, August and European Heritage Days.

The tumulus is on a hill called "Boss of Prayer", about 6 km west of the centre of Saint-Nazaire and 3 km from the coast. It is surrounded by natural landscapes, between the estuary of the Loire and the Atlantic Ocean, and is located near the road of Dissignac, near the old road of Saint-Nazaire to Guérande.

The site was first dug up in 1873 by A. Martin and R. Kerviler, and was the subject of extensive archaeological campaigns in the 1970s and 1980s, led notably by Jean L'Helgouach. These excavations revealed a construction in two stages: a first phase with a 17 m diameter enclosure, followed by an extension to 21 m with the addition of two additional enclosures. The funeral chambers, one semicircular and the other rectangular, are accessible by two parallel corridors facing southeast.

The slabs of the burial chambers come from the coast, some having been transported over 4 km. Bedroom 2 contains a slab engraved with motifs similar to those of the Morbihan megaliths, such as triangular axes and buttocks. These engravings, made by picketing, bear witness to cultural exchanges between the regions. Archaeological material discovered during the 1970s-1980s excavations included ceramics (bols, cups, vases) and stone tools (haches, scrapers, arrow tips), dating back to the fourth millennium BC.

The tumulus consists of a cairn 3.20 m high, covered with vegetated soil, and surrounded by three concentric enclosures. The first, 2 m high, is in local gneiss; the second combination of granite, quartz and pebbles; The third is a simple stone wall. The space between the enclosures is filled with piers, and a wall façade was added between the entrances during the second phase of construction.

Owned by the state, Dissignac's tumulus illustrates the megalithic architecture of the late Neolithic and Chalcolithic era. His study provided a better understanding of funeral practices and construction techniques of that time, as well as networks of exchanges between prehistoric communities in western France.

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