An chathair dhraíochta - would it be?

Looks ok to me. You could also say cathair faoi dhraíocht if you wanted to say that the city is "enchanted" or "under a spell."

Go raibh maith agat, a chara.

I think I’d say cathair na draíochta instead of an chathair dhraíochta. Sounds more natural to me.

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Not a native speaker.

Always wait for at least three people to agree on a translation, especially if it’s for something permanent.

My translations are usually GU (Ulster Irish), unless CO (Standard Orthography) is requested.