Moreover, there were two of these incredible guns.
It has been manufactured by Krupp for the third Reich during WW-2.
Hitler wanted "a gun able to pierce a meter of stell, seven meters of concrete, or thirty meters of dense earth".
As you can see, it's a railroad gun.
But it's so large that two railways are just enough to ensure stability and weight distribution.
Three calibers could have been used: 700, 800 and even 1000 mm ! The Oberkommando Heer conducted the fisrt tests of these enormous guns during 1935, for the growing Reich.
You must know that railroad guns where very numorous during WW-2: they represented mobile high-power artillery.
Before the Dora, the largest of these were 280 mm units. The design of the gun, which was very demanding, ended in 1937.
Even now, we can hardly imagine how we could manufacture the enormous 290 tonnen barrel, an huge steel pipe, 32 meters long.
Monobloc trunion craddles, on which are put the trunion pins of the barrel, are as tall as a 4-floor building : these oversized parts needed long preparation, and initial delivery date during spring 1940 could not be met.
The gun was ready in '41, and undergone testing at the Hillersleben training ground.
It was ready for action in late 1942.
Unfortunately (for the gun), all its targets where almost down or captured at this time: the Maginot line, Gibraltar...
The only target the Dora crushed was Sevastopol. During five days, the gun shot 48 shells over 7 targets.
Its monstruous power put down the forts of the town, delivering never seen damage at each shot.
You know the "bang" a rifle does, so try to imagine the sound of apocalypse when a 7 ton shell is fired, using thousands pounds of gun powder, enough to send it dozens of miles away...
This is not sci-fi, this was the madness of a tyran, and probably the most outstanding achievement in conventionnal balistics.