The open ammunition storage at the airfield has been modified after the war. Having some expertise on Cold War constructions, I think that the French used this bunker as a very well protected storage. We did not find any active components such as power cables or ventilation. So it was not ment as a save haven for the "Mona Lisa" in bad times.
The central room has been transfered into a genuine vault. The date is eight years before the fall of the Berlin Wall.
This is a heavy door. It was closed with many sliding steel bars.
The rooms besides the vault have steel beams to reinforge the neighbouring compartments.
Even this relatively small room has this feature.