This is a statue by Cesar, the man who made himself a fortune and a name in the modern art history by compressing cars. To be more accurate, this thumb is his, cast and disproportionnately oversized. Just as the artist's "ego".
We are not really fond of this thumb, but we mention it nonetheless.
It is located in the frontyard of the City hall, in the old town. (5 rue de l'Hotel de Ville.) You can see it from the street even if the gates are closed. Your children (under 6) will probably enjoy it...