Wonderful castle right in Nantes. You can enter the courtyard via several directions - no fee. An exhibition is in one building and the museum in the chateau part. The lady at the front desk was not very helpful but eventually we determined that we only wanted a ticket for the museum part not both (can buy combined). The museum is housed over all the floors of the chateau and gives a pretty good overview of the history of Nantes and Brittany until the present. Almost all displays and video are in French only but in each of the 30 rooms there is a large book that explains the premise behind that rooms' displays in several languages. It was pretty interesting but I didn't like that just about all the windows were sealed, closed, shuttered or curtained and it was quite dark. There are many steps to walk both up and down although a handicapped lift is available. If you have the time & find the information interesting you can spend 1 to 2 hours in here. If you're short on time I would recommend skipping both the museum and exhibition and just admire the castle from the courtyard, from outside the walls and from the castle ramparts walk of which access is provided free of charge.
If you own or manage Chateau des Ducs de Bretagne, register now for free tools to enhance your listing, attract new reviews, and respond to reviewers.