I don’t know too many German films. But “The Spessart Inn ” and “The Haunted Castle” are familiar even to me.
Spessart are wooded mountains, quite high in places, located between the A3 and Main and further beyond the A3 towards Fulda. Through the Main to the south, the mountains continue, but are already called Odenwald. And Odenwald then goes to the Black Forest. And it turns out such an extended mountainous-wooded strip up to Switzerland.
The name Spessart in its original form meant “woodpecker mountainous forest”.