Gustav railway gun

Developed in the late 1930s, the Schwerer Gustav was a massive siege railway gun used to destroy heavy fortifications. Weighing over 1,350 tonnes and firing shells that weighed 7 tonnes, the Schwere Gustav was capable of firing over 47 kilometers (29 miles). In this photo, Adolf Hitler and other high-ranking Nazi officials are seen reviewing the massive Gustav railway gun before it was deployed to the Russian front, circa 1941-1944. The photo is impressive with people around it to give it some scale, however, the real thing must have been awesome to gaze upon.The technology is now considered obsolete as it has been surpassed by aircraft and rocket payloads. (Source)