Nizhni Novgorod vs metropolis

Nizhni Novgorod and metropolis both are nouns.

Word	Noun	Adjective	Verb	Adverb
Nizhni Novgorod	Yes	No	No	No
metropolis	Yes	No	No	No

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