I would call Saint-Malo the younger brother of Mont-Saint-Michel. Both there and there the main character is a town imprisoned inside the fortress, and the main attraction is the ocean tide, cutting off access routes for several hours. The distance between cities is only 50 km.
Of the four districts of Saint-Malo, the most interesting is "Intra-Muros", surrounded by a fortress wall, inside which harsh tall houses with harsh high chimneys lined up. Near the fortress - the castle-city hall and several islands, accessible only at low tide. On one of them, a local native of Chateaubriand, writer, politician and steak is buried.