acropolis
bastion
beachhead
blockhouse
bridgehead
bunker
castle
donjon
fasthold
fastness
fort
fortress
garrison
garrison house
hold
keep
martello
martello tower
mote
motte
peel
peel tower
pillbox
post
rath
redoubt
safehold
strong point
stronghold
tower
tower of strength
ward
Kremlin
abbey
arsenal
barrack
battlements
bulwark
cathedral
cavern
chateau
edifice
fortification
monastery
mosque
pagoda
palisade
rampart
sanctuary
turret