The train cannon that shot 7 ton shells!
I also think it's not fair how every main country like America has copied thier designs and are claiming them and using them as today's standard, what I mean by this is the Germans were well ahead of thier time in the war!
As we can see that is a German stealth plane from world war 2 and many other country's have copied it in Modern society, the point is the Germans were well advanced for time .
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From @jameskray