down town vs civic center

down town and civic center both are nouns.

Word	Noun	Adjective	Verb	Adverb
down town	Yes	No	No	No
civic center	Yes	No	No	No

As nouns, down town and civic center are synonyms defined as:

Other synonyms of down town include municipal center.

down town (noun)	civic center (noun)
the center of a city	a center where the members of a community can gather for social or cultural activities
	the center of a city