Castle Wittgenstein sits on cliffs above the village of Wittgendorf on the west bank of the river Reik, a day's sailing upstream of Kemperbad
It has an evil reputation, according to Gertrude Grolsch who you met on Aubentag 7th Sommerzeit just before you passed the castle.
You believe that Dagmar von Wittgenstein brought the warpstone meteorite he found in the Barren Hills to the castle in the year 2402.
On Marktag 7th Vorgeheim you located a secret way in to the castle via a cavern under the outer bailey.