metropolis vs Rostov-on-Don

metropolis and Rostov-on-Don both are nouns.

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

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