A military bunker located near Ketrzyn, Poland, built during World War II when the area was part of German territory (then called Rastenburg). This structure follows the German Regelbau B1-1 design, which was a standardized bunker type used by Nazi Germany for various military purposes. The bunker was constructed in 1942 as part of Germany's defensive fortifications in the region.
These Regelbau bunkers were typically used as splinter-proof shelters to protect personnel from bombing raids and artillery fire. The area around Ketrzyn saw significant military construction during the war due to its strategic importance in East Prussia.