Herculaneum vs urban center

Herculaneum and urban center both are nouns.

Word	Noun	Adjective	Verb	Adverb
Herculaneum	Yes	No	No	No
urban center	Yes	No	No	No

Herculaneum (noun)	urban center (noun)
ancient city; now destroyed	a large and densely populated urban area; may include several independent administrative districts