Nizhnyi Novgorod vs urban center

Nizhnyi Novgorod and urban center both are nouns.

Word	Noun	Adjective	Verb	Adverb
Nizhnyi Novgorod	Yes	No	No	No
urban center	Yes	No	No	No

Nizhnyi Novgorod (noun)	urban center (noun)
an industrial city in the European part of Russia; birthplace of Maksim Gorky	a large and densely populated urban area; may include several independent administrative districts