C'harr-tan #7 is a group of Corbin Merlin roadsters with Harley-Davidson engines, and Breizh #2 is the "Tombeau de Merlin" (Merlin's Tomb), the remains of a neolithic tumulus near Saint-Malon-sur-Mel in Brittany. Here Viviane, "The Lady of the Lake" is supposed to have imprisoned Merlin, the magician of Arthurian legend, after he had taught her all his magic secrets.
Or it could have been at Marlborough Mound in Wiltshire, UK...