The French Army, since 1952, has stationed an EOD unit at Verdun. Driving a different route every day of the week, they stop along the road and pick up unexploded shells the farmers have found in their fields and stacked by the road.
That stuff will be there for another hundred years, killing and injuring French farmers every year. And all the ordnance the Eighth Air Force and the RAF dumped along the Belgian/ German border, the odd 500 pound bomb that got stuck in the bomb bay they manged to eventually jettison.