#LastBoost
It's not in Nantes per se, since Nantes is not bordering the sea. It's close though. But I have never seen it even though I've been living in -- then near -- Nantes for 13 and a half years.
There are a ton of cool artistic stuff around the Loire estuary from Nantes to Saint Nazaire. If you go to France and want to discover cool stuff I definitely recommend those! If you go a bit east from there, still following the Loire, you'll find a bunch of cool castles that were built for french Royalty : Chambord, Chenonceau, to cite the most well-known here