Hitler ordered the construction of the fortifications in 1942.
Almost a million French workers were drafted to build it.
The wall was frequently mentioned in Nazi propaganda, where its size and strength were usually exaggerated.
The fortifications included colossal coastal guns, batteries, mortars, and artillery, and thousands of German troops were stationed in its defences.
When the Allies eventually invaded the Normandy beaches in 1944, most of the defences were stormed within hours.
Today, ruins of the wall exist in all of the nations where it was built, although many structures have fallen into the ocean or have been demolished over the years.