Walkenried in the south of the Harz mountains is a climatic spa really unique in this world. You can find here:
An interesting, natural landscape full of surprises
A cloister full of history provinding guided tours
Proper hospitality and tasty typcial Harz food
A popular forest open air bath, a mini gulf place, fishing ponds etc.
Clean air and fine walking paths
... and lots more! Just take a tour though this website, it will be worthwhile!