The Battle of Verdun was the longest single battle of World War One.
Fort de Douaumont was the largest and highest fort on the ring of 19 large defensive forts protecting the city of Verdun but still couldn't be adequately defended against the German guns.
The Germans captured Fort Douaumont on 25th February, 1916 without a contest.
The Colonial Infantry Troops of Morocco eventually recaptured the fort on 24th October, 1916.
There are some pleasant walks around the old concrete bunkers and tourists can visit inside the fort.