Dora Gun was manufactured by the German company Krupp for the third Reich during World War II. Hitler had wanted a gun "able to pierce a meter of steel, seven meters of concrete, or thirty meters of dense earth": Link - Thanks Sammy and gahsoon!
That is one badass gun tho, the shell is taller than a human being.
There's also the V3, another large nazi cannon. While the bore was 'only' 15cm/6in it was 150m long, compared to the 36m of dora. It was designed to fire on london from it's position deep in a bunker in france.
Well , dont know about anyone else but I'm still hugely disappointed that there is no such thing as a giant robotic russian gun patrolling its borders. curse you photoshop for your oh so realistic imaging trickery!!!
Silly fox...
http://www.astronautix.com/lvs/babongun.htm
http://www.geocities.com/pentagon/2833/wunderwaffen/supergun/v-3/v-3.html
http://www.amazon.com/My-Tank-Fight-Zack-Parsons/dp/0806527587
random factory