The Sigmund was a German 280 mm railway gun built by the Krupp steelworks. It was dispatched in South Italy in 1943 along with its more famous sister gun, the famed Anzio Annie. Used to bomb partisan strongholds from the Regilino Viaduct, the K5 railway gun was plunged into a chasm when SOE operative Karl Fairburne blew up the viaduct underneath it. Interestingly, Krupp K5 280 mm railway guns are based on the Skoda 280 mm guns of the Scharnhorst class heavy cruisers whose main turret, without the central gun, was mounted on the P.1000 Ratte super heavy tank featured in Sniper Elite 3.
(Despite this page name, the Sigmund is not a Schwerer Gustav, being nearly 4 times smaller than the behemoth 800 mm cannon)