Visited this on a cycling holiday in Brittany this summer. Just before the bend in the D7 going out of Saint-Suliac, walk up the farm track to the right, and you will see a home-made sign to "Menhir". That leads you into an orchard (there was nobody around when we were there) surrounding this massive stone. It is a very rugged and irregular shape. Whether really a menhir or just a prominent erratic I know not, though the maps show it as prehistoric. There was a huge pumpkin nearby with the name Gargantua carved into it. Menhir a true word spoken in jest, as Obelix might have said (in English translation).