acropolis vs bastion

acropolis and bastion both are nouns.

Word	Noun	Adjective	Verb	Adverb
acropolis	Yes	No	No	No
bastion	Yes	No	No	No

As nouns, bastion is a hypernym of acropolis; that is, bastion is a word with a broader meaning than acropolis:

acropolis: the citadel in ancient Greek towns
bastion: a stronghold into which people could go for shelter during a battle

Other hypernyms of acropolis include citadel.

acropolis (noun)	bastion (noun)
the citadel in ancient Greek towns	projecting part of a rampart or other fortification
	a stronghold into which people could go for shelter during a battle
	a group that defends a principle