From the Introduction:
Ever since the first bombard was put into service the storage of ammunition has been a unique problem. Modern artillery shells aren't as volatile as kegs and cast iron balls filled with black powder used to be, but their handling still demands extraordinary care and attention. Another problem was posed by artillery and other modern weapons. They made older fortifications pretty much obsolete and at the same time stores filled with ammunition have become prime targets.
This bunker is an example for modern ammunition storage taking these things into account. Its walls, as well as floors and ceilings are made of thick steel reinforced concrete, covered with a thick layer of soil and grass, both for additional protection and concealment. A single ramp leads down to the first massive steel door leading into an anteroom from where the actual storage area can be accessed through another such door.
A simple warning sign over the outer access hatch hints at the explosive contents of the bunker and only a few safety lamps provide illumination within, revealing rows of crates filled with mortar and artillery shells of various calibers equipped with a number of different payloads.