If you have the opportunity to visit Nantes, dedicating an hour or two to Les Machines de l'Ile is…read morea must! It's one of the most intriguing museums/showcases/amusement parks I've ever been to, and there's really nothing quite like it in the U.S.
You can ride Le Grand Eléphant, a 4-floor high mechanical elephant that walks around spouting water from its trunk while giving off the occasional trumpet (6,50 €; student price). Additionally, there is an exhibit showcasing the different animal and insect machines built in the past and you have the opportunity to climb onto the first branch of the Heron Tree (6,50 €; student price). The whole Heron Tree is set to be completed by 2018, so that will definitely be a sight to see and explore! I didn't go to the Marine World Carousel, but from the history film shown on the second floor, it seems like a unique carousel for people of all ages.