urban center vs Tucson

urban center and Tucson both are nouns.

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

urban center (noun)	Tucson (noun)
a large and densely populated urban area; may include several independent administrative districts	a city in southeastern Arizona ringed by mountain ranges; long known as a winter and health resort but the population shift from industrial states to the Sunbelt resulted in rapid growth late in the 20th century