abstract
alliance
area
background
barrier
belong
blur
border
boundary
brown
cage
cheerless
close up
cohesion
concept
confinement
connect
connection
cooperation
dark
detail
detention
dismal
fear
fence
forlorn
freedom
gaol
gloomy
grim
helix
hindrance
hopeless
impossible
imprisonment
iron
jail
limit
macro
metal
metallic
no people
nopeople
old
oppression
penitentiary
perimeter
prison
railings
sad
sadness
safety
security
sepia
somber
sombre
steel
symbol
symbolize
thread
together
winding
wire