Dora was a massive World War II German 80 cm K (E) railway siege gun. This is the second of two. The first as call the Schwerer Gustav. They were developed in the late 1930s by Krupp for the express purpose of destroying heavy fortifications, specifically those in the French Maginot Line. They weighed nearly 1,350 tonnes, and could fire shells weighing seven tonnes to a range of 65 kilometres (40 mi). Credit to the artist.
Schwerer Gustav was the name of a German 80 cm railway gun It was the largest-calibre rifled weapon ever used in combat, the heaviest mobile artillery piece ever built in terms of overall weight, and fired the heaviest shells of any artillery piece.