Fortress Schoenenbourg was part of the Maginot Line Frances ill fatted defence against the Germans.
This Fort is amazing, it looks quite small from the outside, but go inside, down 135 stairs (there is a lift, but you are only supposed to use this on the way up) and there is over 1.2km of corridors to explore. These forts were so large they had a train system in them
There is a Power House to generate the forts of Electrical supply, a Hospital complete with Operating Theater.
Kitchens and Food storage.
And of course the guns, you cant see much of them as they are mounted on Hydraulic lifts so they can be lowered when not in use.
The guns are controlled from a separate 'Fire Control' room.
The fort was never overrun and fired 16,000 shells before it surrendered 5 days after the Armistice, in compliance with an order from the French High Command.
If your interested in this sort of thing the €7 per person entrance fee is well worth it.