View of the Le Menec stone alignments with the Saint-Michel tumulus in the distance (top right)

The tumulus was built during the fifth millennium BC. It consists of a mound of earth and stones 125 metres (410 ft) long, 50 metres (160 ft) wide and 10 metres (33 ft) high.[1] Explored in 1862, researchers found there a central vault containing fairly prestigious funerary furniture: axes, pearls, flint tools and sillimanite.

It has been classified as a "Monument historique" (National heritage site) since 1889.

Around 1900, the archaeologist Zacharie Le Rouzic [fr] again excavated the Saint-Michel tumulus and discovered a second dolmen and fifteen small stone chests, thus revealing the complexity of this monument.