abstract
ancient
background
barb
barbed
barbed wire
barbwire
barrier
blue
border
boundary
chain
close
color
concentration
concept
crime
danger
dramatic scene
fence
forbidden
freedom
gloomy
guard
history
iron
jail
low saturation
metal
military
old
outdoor
prison
protection
razor
refugee
safety
second world war
security
sharp
silhouette
sky
steel
symbol
theme
threat
wall
war
war theme
wire