Anzio Annie was I think a 580mm Railgun that the Germans used against the Allied Beachhead at Anzio. It may have even been a 280mm gun but look up Anzio Annie and itll show ya. I copied this from a page that had a model of the gun and all I can find on Wiki is Krupp K5 which just talks about the guns built...
"Anzio Annie" was the name of the German railroad gun that was used against the American troops during the amphibious landings at Anzio, Italy during World War II. The huge 28cm gun fired 550 lb. shells up to 60 kilometers, and our troops never did destroy, or in any way cripple Annie. The German artillerymen put Anzio Annie out of commission. Today, it can be seen at the Aberdeen Proving Grounds Museum, Aberdeen MD.