Sandun dolmen, dolmen in Guérande, France

Sandun dolmen is a ruined gallery grave in Guérande, France, standing about one meter tall on a small hill overlooking the Brière wetlands. Its remaining upright granite stones form a rough rectangle, while many of the original covering slabs now lie on the ground or are hidden by plants.

The gallery grave was already partly damaged when Henri Quilgars excavated it in 1896; he found seven standing stones, the tallest about one metre, in a rectangle roughly 7.5 m by 1.5 m, with the entrance to the east. The covering slabs had long vanished, and an eighth orthostat was uncovered during the dig. The monument was classified as a historical monument in 1935.

The name Sandun also belongs to the Croix de Sandun, the cross that gives the dolmen its alternative name. The monument is stop number 3 on the Route Bleue, a driving route linking eleven prehistoric megaliths between Saint-Nazaire and the Pays de Retz, alongside the tumulus of Dissignac and the menhirs of Bissin and Pierre Attelée.

The site is outdoors and fully exposed to sun, wind, and rain, so comfortable shoes and weather-appropriate clothing make the visit easier. The ground can be uneven around the fallen stones, and the low hill offers a clear view over the surrounding marshy landscape below.

The 1896 dig revealed large fires with ashes and charcoal inside the chamber, along with two rough pottery vessels, one black and one red. Nearby, a 1987 excavation uncovered traces of a small Neolithic village, suggesting the people who used this tomb lived just a short walk away.