Food supplies are vital in any invasion. When the German Wehrmacht marched into Copenhagen in April 1940, they seized control of Kødbyen (the Meatpacking District), home to the city’s abattoirs and food processing facilities.

The bulky, symmetrical building known as the “Twin House” at the Northernmost edge of Kødbyen housed the Nazi forces’ potatoes, a crucial source of carbs. Soldiers kept the stock of stored potatoes under a 24-hour surveillance.

As they soon learned, guarding potatoes in a largely peaceful country wasn’t very exciting. They began to scratch words into the bricks of the Twin House so that now, decades later, people can read the thoughts that passed through their bored minds.

Most of the messages are what you’d expect: names of loved ones and hometowns, drawings, and other tributes to home. But some allow us a closer look at how the soldiers tracked their time. “Weihnachten auf Posten 1943” (Christmas on guard duty, 1943) reads one glum brick. Another guard had scratched the date of his guard duty (August 1st, 1940) only to return almost exactly two years later to add the date August 4th, 1942 to his brick.

Toward the end of the war, you can see the soldiers’ disillusion in solid brick form. One soldier scratched the words from Goebbels’ famous Sportpalast speech, “Wollt ihr den totalen Krieg?” (Do you want total war?) which had been followed by a roaring YES! at the Nazi rally. The guard on duty didn’t agree. On the brick wall, a small “nein” is scratched below the propaganda minister’s words—something that would have gotten a German soldier into a lot of trouble.

Oddly enough, this piece of history doesn’t have protected status. New graffiti is added to the walls from time to time and as these age and darken, it becomes difficult to spot the difference between a half finished “Stuttgart” (probably abandoned because a commanding officer showed up) and a neo-Nazi swastika from last year.