"Do you want to go to the pub?"

Translation: Dych chi eisiau mynd i'r dafarn?

[ellenkeyne]

Since we haven't been formally introduced to mutations yet, "i'r dafarn" feels a little unfair!

[romankiw]

I agree. If anything, it should give you "i'r tafarn" as a correct answer, but call it a typo.

[allenfrang]

So, from what a I gather, when going to a named place like another town, or "chapel", you don't use the definitive, but otherwise you do translate and use the definite as it is.