It was like that near Arles in April (2007), a dolmen marked on the map, I tried approaching it by car and it was on private gated land,..... If one had the time (which I didn't), one could try different approaches to the site, via fields or woodland....

There's a bit of a problem with regards to the lesser known archaeological sites in France, to put it mildly... neglect ,ignorance, and a total lack of interest. The same thing applies to loads of isolated medieval churches, which are falling into ruin, (the money or interest just isn't there to restore them.....)