Those bunker reminds me of an expo near Paris, on the fortifications built around Paris between the Franco-Prussian war of 1870 and WW1. The idea was coming fro

Those bunker reminds me of an expo near Paris, on the fortifications built around Paris between the Franco-Prussian war of 1870 and WW1. The idea was coming from the siege of Paris during the 1870 war and the French army built a ring of forts around Paris, at great cost. And all those forts ended up outdated when the next war with Germany arrived.