Christiania vs Oslo

Christiania and Oslo both are nouns.

Word	Noun	Adjective	Verb	Adverb
Christiania	Yes	No	No	No
Oslo	Yes	No	No	No

As nouns, Christiania and Oslo are synonyms defined as:

Christiania and Oslo: the capital and largest city of Norway; the country's main port; located at the head of a fjord on Norway's southern coast

Other synonyms of Christiania include capital of Norway.

Christiania (noun)	Oslo (noun)
the capital and largest city of Norway; the country's main port; located at the head of a fjord on Norway's southern coast	the capital and largest city of Norway; the country's main port; located at the head of a fjord on Norway's southern coast