urban center vs Rio de Janeiro

urban center and Rio de Janeiro both are nouns.

Word	Noun	Adjective	Verb	Adverb
urban center	Yes	No	No	No
Rio de Janeiro	Yes	No	No	No

urban center (noun)	Rio de Janeiro (noun)
a large and densely populated urban area; may include several independent administrative districts	the former capital and 2nd largest city of Brazil; chief Brazilian port; famous as a tourist attraction