Norway had quite a few as well.
When I was there back in 1989, there were zones still closed because of Landmines.
However expected to clear gradually due to the activity of wild pics. KABOOM-Squuueeeel
Lots of those as well on the old Siegfried line, looked at some near Saarbrucken some years back. Quite interesting. Those are however filling with soil, leaves and wildlife in general, so step down carefully....