Rostov-on-Don vs metropolis

Rostov-on-Don and metropolis both are nouns.

Word	Noun	Adjective	Verb	Adverb
Rostov-on-Don	Yes	No	No	No
metropolis	Yes	No	No	No

Rostov-on-Don (noun)	metropolis (noun)
a seaport on the Don River near the Sea of Azov in the European part of Russia	people living in a large densely populated municipality
	a large and densely populated urban area; may include several independent administrative districts