urban center vs Motor City

urban center and Motor City both are nouns.

Word	Noun	Adjective	Verb	Adverb
urban center	Yes	No	No	No
Motor City	Yes	No	No	No

urban center (noun)	Motor City (noun)
a large and densely populated urban area; may include several independent administrative districts	the largest city in Michigan and a major Great Lakes port; center of the United States automobile industry; located in southeastern Michigan on the Detroit river across from Windsor