Myself and my then GF visited Arras just north of Verdun in 2019. She was a few months pregnant at that stage and in every hotel we stayed, the proprietor warned her to only drink bottled water, including for brushing teeth.

The locality got so hammered with poison gas shells, it all seeped into the ground water making it mildly poisonous!!

Lovely part of the world, but a sad legacy of military buildups.