In December 2007 I was in the area, so I went to visit this location. I did not really think of it as very exciting, because bunkers do not attract me that much. However if you like them this is your heaven.
After Adolf Hitler conquered France and the Low countries, he searched for a place for his new West front Head Quarters. From this HQ he wanted to lead the invasion of Great Britain, operation Seelöwe. The complex was build close to the area were he went to battle in the First World War. However, this invasion of Britain never occurred. He only spent a few days on this HQ when the allies invaded France after D-day. After the war the location was used by the French Army. It still is property of the French army, but a company uses the site to store explosives. The terrain is a forbidden area, and the French military has quite harsh punishments for offences.