urban center vs Sao Paulo

urban center and Sao Paulo both are nouns.

Word	Noun	Adjective	Verb	Adverb
urban center	Yes	No	No	No
Sao Paulo	Yes	No	No	No

urban center (noun)	Sao Paulo (noun)
a large and densely populated urban area; may include several independent administrative districts	an ultramodern city in southeastern Brazil; the largest city in South America