This neolithic allée couverte at Mougau Bihan dates from c3000. It has an entrance in the north, a corridor to the burial chamber (without significant distinction) and a small separate cella (front in photo). The giant roof slabs would once have been covered with earth and grass. Inside are carvings of paddles/threshing implements, goddess breasts (raised pairs of dots - I can't really believe in that interpretation) and a hafted axe on the wall of the chamber. The latter, like so many other 'pagan' monuments in Brittany, was daubed with Catholic symbols in flourescent pink paint soon after the new pope's anti-pagan speech. Truly enlightened behaviour.
Theories of an inverted boat-shape for such tombs may explain the oar or paddle type carvings, as necessary props for the soul's final progress across water, presumably accompanied by a psychopomp.