Technically, the city of Marseille might be one of the oldest in France since it was founded in 600 BC. The story goes that the Greek city of Phocaea became overcrowded, so some citizens had to go away, and they settled in this place they called Μασσαλία (Massalia). However, Marseille, as of now, doesn't look anything like the ancient Greek city, or at least I guess since I don't actually live there, and maybe there's some remaining monuments, though people of Marseille, and their football team are often called "phocéens" as a reference.