mru world war ii fortification bunker, pniewo, near miedzyrzecz, poland. entrance to the underground corridor system. german milit

above aerial area army background bunker bunkers concrete construction corridor corridors defense dome domes drone dzyrzecz entrance environment europe field fortification fortifications from german green ground history landscape line metal miedzyrzecz milit militarized mià mru one outside plant pniewo poland rural shelter sky spring strengthened summer system tree underground view war world zone