Yeephang W.
Google
Very beautiful memorial underground with some work also embedded in the pavements leading to it, subtle but powerful message.
There are two entryways, the starting point is by the Pont Anne de Bretagne (or the Chantiers Navals stop if taking tram #1), and there is a lift for those having mobility issues.
For in depth understanding of this there is recommendations to got to the musée d'histoire de Nantes, located in the Château des ducs de Bretagne.