underground storage facility built into stone hill, brick wall and iron door, oscarsborg fortress, historic ww2 site in norway

bak black brick built corrosion county defense door dracedil europe facility ferrous footpath fortress fungi green growing growth hiding hill historic iron islands kaholmen metal moss mountain narrow nature norway norwayn oscarsborg oxides path plant red rock rust rusty scandinavia season secret site sound stone storage summer texture tourism trail transportation travel underground vacation vertical viken wall war world ww2