The tumulus of Saint-Michael was constructed between 5000 BC and 3400 BC.
At its base it is 125 by 60 m (410 by 200 ft), and is 12 m (39 ft) high. It required 35,000 cubic metres (46,000 cu yd) of stone and earth. Its function was the same as that of the pyramids of Egypt: a tomb for the members of the ruling class. It contained various funerary objects, such as 15 stone chests, pottery, jewellery, most of which are currently held by the Museum of Prehistory of Carnac.
It was excavated in 1862 by René Galles with a series of vertical pits, digging down 8 m (26 ft). Le Rouzic also excavated it between 1900 and 1907 discovering the tomb and the stone chests.
A chapel was built on top in 1663 but was rebuilt in 1813, before being destroyed in 1923. The current building is an identical reconstruction of the 1663 chapel, built in 1926.