Carnac is probably one of the most famous places in Brittany for its incredible amount (4000!) of magalithic standing stones. Usually we don't like touristic places, but this one is a must. A few hours are enough to visit Carnac.

"Carnac is 6000 years of history and archaeology inscribed in its stones and in the ground surrounding them, it is this that constitutes the megalithic monument." (from a brchure of the visitors centre)