Le Mans Museum - located at the Circuit de la Sarthe main entrance and is one of the 'must do' visits for anyone who hasn't previously been to Le Mans.
Housing a unique collection of the first road-going cars in history to a very fine collection of Le Mans race cars from over the years.
Having visited many times it appears that it is possible to not have noticed all the exhibits the first or even the second time around. In addition, new vehicles are occasionally being added to the collection, so it is never the same experience twice and certainly worth revisiting, even if you have been there before.
Link for further information: https://www.lemans-musee24h.com/en/