You can find three five thousand-year old (estimated date of construction c3500BC listed on the French state department information board) dolmens at Mane Kerioned. - two are side by side, and one, probably earlier, is at right-angles to them. It's worth bringing a torch to see the carvings on some of the stones within the dolmens, which are best seen when the light is held at an angle to the stone. You can see the dolmens from the D768 travelling south - though by then you've already passed the turning to the right to the car park. The dolmens of Keriaval are nearby, though unfortunately on the other side of the fast D768 highway. Se the Keriaval site for a schematic map.