I am confused by the following example sentence

Question

Luis told me where he had gone on holiday. : Luis me dijo ___ había ido de vacaciones.

The stated answer is “dónde” (with an accent), but this usage seems to be that of a relative pronoun. What am I missing? Why is it “dónde” (with an accent)

Answer

Hi Devon, 
In this case you cannot translate "dónde" into "in which", therefore it is not a relative pronoun but an indirect interrogative. There is a box at the bottom of the lesson giving you this tip:
Remember:
Dónde = where = "in what location" (interrogative and exclamatory pronoun).
Donde = where = "in which" (relative pronoun in subordinate clauses).
I hope it clarifies your doubt.
Inma

Answer

Thank you!