An opening in the wall of a fortress through which the guns are levelled; a narrow loophole through which arrows and other missiles may be shot.
A tower at the entrance to a castle or fortified town
A fortress at the end of a bridge.
A temporary wooden tower built for defensive purposes.
A sturdy military fortification, often of concrete, with gunports.
A reinforced building from which to control hazardous operations, such as an explosion or a rocket launch.