urban center vs Nantes

urban center and Nantes both are nouns.

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

urban center (noun)	Nantes (noun)
a large and densely populated urban area; may include several independent administrative districts	a port city in western France on the Loire estuary