urban center vs San Sebastian

urban center and San Sebastian both are nouns.

Word	Noun	Adjective	Verb	Adverb
urban center	Yes	No	No	No
San Sebastian	Yes	No	No	No

urban center (noun)	San Sebastian (noun)
a large and densely populated urban area; may include several independent administrative districts	a city in northern Spain on the Bay of Biscay near the French border; a fashionable seaside resort