I'd assume there is one in Pas-de-Calais.
Why play there instead of Lille?
Well the total population of the main conurbation (Béthune to Hénin-Beaumont, centered on Lens) is around 500,000 or so... we aren't talking a bunch of villages here, but a lot of large towns that have merged together into a single urban unit (while each also retains its own sense of self to an extent). So that would be a reason. And then you have Calais which is a big town with over 70,000 people, as Boulogne-sur-Mer and Arras (both over 40,000 and the latter is a service centre for a wide rural hinterland) so...