Tw3 achievements bookworm unlocked
"Do you really wish to know?"
Spoilers from the books and/or games to follow!
Zurbarràn is a castle in Toussaint, located on the hill near Pomerol castle. It is known for the uncharted network of caves which Geralt of Rivia had undertook to explore during the Lady of the Lake novel.

By coincidence, he discovered the secret meeting of Nilfgaardian opposition plotting against the Emperor Emhyr and also learned about Vilgefortz' current location.