Château des Ducs de Bretagne

Forget fusty furnishings – light-filled rooms inside the Castle of the Dukes of Brittany house multimedia-rich exhibits detailing the city's history. Look out for sobering documentation of the slave trade, and vintage scale models of Nantes' evolving cityscape. The chateau's grassy moat gardens and rampart walk are free to meander and picnic in at leisure. Don't miss the playful summertime slide, built snug against the 15th-century ramparts, by contemporary Breton artist Tangui Robert. Who wouldn't want to whoosh down it? Chateau admission includes temporary exhibitions too; audioguides (€2) can be rented at the front ticket desk.