Why Did This Town Die?
Wikipedia claims that the port of Fecamp's growth eclipsed St. Valery's over time, but I can't imagine a better geographical location this: a harbor linked to a fresh water river, high cliffs for defense, wide rocky beach and bountiful fishing right offshore. The harbor itself curls around those high cliffs like a question mark meaning the inner harbor is fully protected from North Sea storms and medieval pirates. I would have thought the town might have grown immensely over the years.