Hitler inspects the Schwerer Gustav (English: Heavy Gustav), the largest rifled artillery ever deployed in combat, that fired 7 ton, 800mm shells. The gun was named after Gustav Krupp, the senior director of the company that built it. The thing was so large that it required mounting on parallel sets of railway tracks. It only ever saw use in June, 1942 during the siege of Stevastopol, where it wore out the barrel after firing only 48 rounds, a scant number compared to the roughly 250 test rounds fired before it was deployed. The gun was destroyed on purpose to prevent capture in 1945.
As the old saying goes, the first one is free. The Krupp company gave this weapon to the German army gratis. It’s sister gun – Dora (named for the senior engineer’s wife), cost the Germans several million Reichsmark but never saw combat.