18the century abandoned army base defense Dutch water line fortress military stairs stronghold The netherlands tunnel wall abstract backgrounds bare bark brown bumps close-up colors colours contrast cracked cracks dark dry edge edges gnarled gray grey grooves layers light lined lines mottled patterns perspectives ridges rough shade shades-of-colour shadows shapes strips sunlight surface surfaces texture textured textures tree tree-trunk trunk uneven wallpaper wood wrinkled wrinkles wrinkly angle angled angles architectural architecture blinds color colored colour coloured curved curves decoration decorative diamonds distinctive elements frontage geometric geometrical glass glass-panes lighting panes rectangles rectangular round shape shaped sunshine surfaced views window-frame window-frames window-panes windows along Australia below conditions construction development direction empty empty of traffic highway highways lamp-posts landscape left-hand driving looking down main road no motor cars no motor vehicles no vehicles road road rules roadwork roadworks signs stop stopped suburban suburbs traffic traffic flow traffic lanes warning wide wide road