On the Neolithic site of Bénaix - known as Morenci
The "roc de la Fougasse" (Fougasse rock), accessible via a narrow path through the undergrowth of a beautiful beech forest, is a rock on which a perfect circle 1.10 m in diameter has been carved. This stone circle is almost certainly an unextracted millstone. Also worth seeing in Montferrier, at a place called La Peyregade, is the sacrificial stone.
Free access.