Henri Salmi (.
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Smallish but really interesting arcahelogical museum, that is undergoing renovation in December 2025. Really informative and lots of information about Aosta's past. You can walk in a real archealogical site in the basement.
There could be more texts in English, though - that was a drawback. But definutely a place worth visiting. The entrance fee is only 5 euros for an adult and it covers also the criptoportico and San Lorenzo too - so it is really a bargain (especially since the ticket is valid for a longer period, so you can visit on separate days the different places)