urban center vs Nanjing

urban center and Nanjing both are nouns.

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

urban center (noun)	Nanjing (noun)
a large and densely populated urban area; may include several independent administrative districts	a city in eastern China on the Yangtze River; a former capital of China; the scene of a Japanese massacre in the 1930s