Cromlech de Kergonan is a Neolithic stone setting on Ile-aux-Moines, arranged in a half-circle of 24 stones. It has been listed as a historic monument since the 19th century and is part of the wider megalithic landscape around the Gulf of Morbihan.
The site is small, but rewarding if you like prehistoric places. See it while walking the island rather than treating it as a standalone excursion from the mainland.