metropolis vs Nizhni Novgorod

metropolis and Nizhni Novgorod both are nouns.

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

metropolis (noun)	Nizhni Novgorod (noun)
people living in a large densely populated municipality	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