Bad Herrenalb is a spa town located in a deep, wooded valley in the northern Black Forest, about an hour by streetcar out of Karlsruhe.
From the website:
Bad Herrenalb offers an extended and well sign-posted network of more
than 150 km of hiking trails into the surrounding valleys and up to
the Black Forest hilltops - magnificent panoramic views and
unforgettable encounters with nature are guaranteed!
I've spent over 2 weeks (16 nights) in Bad Herrenalb in 4 trips. Not only is there great hiking in the area, with the Konus Card that comes with staying there, you can travel by bus to other towns, Bad Wildbad, Calw (Steppenwolf author, Hermann Hesse's hometown), Baden Baden, or Freudenstadt. It also has it's own Therme (Spa), but it's a traditional German Therme, that is, the saunas, steam room, etc., are "Kleiderfrei".