Cologne vs Koln

Cologne and Koln both are nouns.

Word	Noun	Adjective	Verb	Adverb
Cologne	Yes	No	No	No
Koln	Yes	No	No	No

As nouns, Cologne and Koln are synonyms defined as:

Cologne and Koln: a commercial center and river port in western Germany on the Rhine River; flourished during the 15th century as a member of the Hanseatic League

Cologne (noun)	Koln (noun)
a commercial center and river port in western Germany on the Rhine River; flourished during the 15th century as a member of the Hanseatic League	a commercial center and river port in western Germany on the Rhine River; flourished during the 15th century as a member of the Hanseatic League