access
architecture
background
barbed
barbedwire
barbs
barred
barrier
blue
boundary
brick
building
cell
criminal
danger
empty
escape
fence
forbidden
frame
freedom
gaol
grid
guard
jail
light
mesh
metal
nobody
old
oxford
penitentiary
perimeter
prison
private
protection
razor
safety
security
sharp
sky
steel
stone
structure
texture
top
uk
wall
window
wire