The Cairn de Gavrinis is a 6,000-year-old chambered tomb on the small island of Gavrinis in the Gulf of Morbihan. The structure is a 50-metre-wide cairn of stones containing a 14-metre passage leading to a corbelled burial chamber. What sets it apart from every other Neolithic tomb in Europe is the extraordinary density of carvings on the stones lining the passage and the chamber — abstract spirals, snake-like patterns and recognisable axe-heads, all chipped into the granite with stone tools.
Access is by boat from Larmor-Baden between April and November. Visits are by guided tour only, limited to small groups; book ahead. The boat ride across the gulf adds to the journey.