The Musée de Préhistoire de Carnac is one of the best prehistoric archaeology museums in France and an essential companion to the alignments outside. The collection covers the entire Neolithic and Bronze Age sequence of the Morbihan region, with excavated objects from the tumuli and alignments: polished stone axes, gold jewellery, pottery, and engraved stones that give some sense of the culture that raised the menhirs.
The museum does an honest job of acknowledging what is not known about the builders' intentions — the uncertainty about the alignments' purpose is presented as a genuine mystery rather than papered over with a confident theory. Allow 90 minutes to two hours. It is housed in a fine 17th-century building in the centre of Carnac town and is open daily in summer, with reduced hours off-season.