blue
border
camp
construction
defend
escape
facility
fire watchtower
forest
guard
high
hill
ladder
land
lookout
lookout tower
metal
military
monitoring
national
nobody
observation
observe
peak
point
protect
protection
protective
ranger
secure
secured
security
silhouette
sky
station
steel
structure
surveillance
tall
top
tower
view
watch
watching
watchtower