Sorry but - how to send anything to a camino pilgrim?

Hi, I'm a 20 old hungarian girl, my groom is on the Camino, he will arrive to Santiago de Compostela at 29th jule.

I would like to send him a letter to there, and I dont know to what address I could post it, where he certainly can get it.

Can you advice me something?

Thanks for your help,

the best wishes for all:
Victoria