Sao Paulo vs urban center

Sao Paulo and urban center both are nouns.

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

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