The red zone has pretty much been cleared in urban areas. I actually live exactly in it, west of Lille, and all the area is either built up or farmed. I believ

The red zone has pretty much been cleared in urban areas. I actually live exactly in it, west of Lille, and all the area is either built up or farmed. I believe it's mostly in the more sparsely uninhabited Aisne and Ardennes that there are still no-go zones. In the Nord they are less common (though they do exist, like around Vimy). I think WWI leftover ammunition in the north is actually less a problem today than all the unexploded US and British bombs from WWII (which are usually around city centers).