The cost of that weapon must be equal to the cost of whole Dutch Army. If that thing is not extremely accurate, it is a waste. I can't imagine a 800mm shell missing its target.
It may seem silly in the here & now, but it was designed to penetrate deep concrete bunkers & such. The problem with it is to find out how accurate it was, one had to build it & fire it. Some designs seem good on paper, but not in practice. Too bad no eyewitness accounts or photos of the targets before & after are available.
At Trondenes Fort in Troms Norway, one battery of the 'Adolf' Gun has been made into a museum. The Adolf gun is 40,6cm calibre. Maximum range is 56km. At the top of its trajectory the shell reach 21800meters. Flighttime is 130seconds. The barrel lost 400grams during each shoot. Making the barrel useless after 200-250 rounds. The staff are good up there and I am quite pleased to see one of Norway's treasures done right. There were no more than three batteries of Adolf guns in Europe. One in France and two in Norway.
There are some excellent photographs of German officers standing amongst Dora damage at (I believe) sebastopol, huge crater where a bunker once stood with most of the fortification lying upside-down beside, can't find 'em right now but will keep an eye out. Cheers, Adam.
The 16" guns from the Iowa were used in Vietnam to clear LZs. One round could create a major landing zone for the choppers. The NVA had some R&R areas back in areas that they thought were immune. AA and SAMs made air delivery risky. Then they brought out the Iowa with a booster rocket shell for the 16" guns. Must have been scary to be a recipient.
Other railway guns were built, but only two of this calibre ( Schwere Gustav and Dora ). They were a fairly specialized piece of kit - each one weighed a total of 1,350 tons and required a 25-carriage railway train to move into position. No nuclear shells were used in WWII and were never considered by the Germans for these guns which fired concrete-piercing and HE shells.