The cut scene at the beginning of the game says that it is set in Aberystwyth in Wales. This place does exist and has a ruined castle which looks similar to the monastery in the game.
Just a small detail: one of the FMVs of the game (the one with strange symbols floating around, when the heroes talk about alchenmy and mysticism) shows circles with Hebrew words engraved: Keter, Khokhma, and Bina. Those words (meaning Crown, Wisdom, and Understanding) are the attributes of God, according to the medieval Jewish mystical teaching, the Kabbala. Amazing, but they actually bothered to dig up 100% authentic and rare historical/occult material. Talk about class!
"Koudelka" features a true historical figure: the medieval Franciscan monk and savant Roger Bacon makes his appearance in the monastery graveyard.