Annwn vs mythical place

Annwn and mythical place both are nouns.

Word	Noun	Adjective	Verb	Adverb
Annwn	Yes	No	No	No
mythical place	Yes	No	No	No

As nouns, mythical place is a hypernym of Annwn; that is, mythical place is a word with a broader meaning than Annwn:

Annwn: (Welsh mythology) the other world; land of fairies
mythical place: a place that exists only in imagination; a place said to exist in fictional or religious writings

Other hypernyms of Annwn include fictitious place, imaginary place.

Annwn (noun)	mythical place (noun)
(Welsh mythology) the other world; land of fairies	a place that exists only in imagination; a place said to exist in fictional or religious writings