You can drive quite close on a dirt track on the edge of the woodland and take a path in. It's quite near a 'Poney-Club'. I don't remember a signpost but this grid ref is correct.
It lies in the thick woodland of the Foret Domenial L'Isle Adam, and is a sunken length of megalithic drystone walling between orthostats, still bearing the weight of four capstones. At the portal end, a carved stone has a kennel hole in it which presumably once had a blocking stone. All round the allee couverte, which is fenced for protection, wild strawberry plants formed a carpet underfoot. A very nice monument.