History:
German 80 cm (31.5 in.) railway gun. It was developed in the late 1930s by Krupp in Darlowo (then Rügenwalde) as siege artillery for the explicit purpose of destroying the main forts of the French Maginot Line, the strongest fortifications in existence at the time. The fully assembled gun weighed nearly 1,350 tonnes, and could fire shells weighing seven tonnes to a range of 47 kilometres (29 mi). The gun was designed in preparation for the Battle of France, but was not ready for action when the battle began, and in any case the Wehrmacht's Blitzkrieg offensive through Belgium rapidly outflanked and isolated the Maginot Line's static defenses, eventually forcing the French to surrender and making their destruction unnecessary. Gustav was later deployed in the Soviet Union during the Battle of Sevastopol, part of Operation Barbarossa, where, among other things, it destroyed a munitions depot located roughly 30 meters below ground level.

Unfortunately, its not working. :(

Source: Wikipedia.

I hope you like this. It took me 6 hours to build.