The Black forest (or at least parts of it) is the last remaining piece of "ancient forest" left in Western Europe. All other forests you'll find in Europe are in fact hand-planted parks, like "the Hoge Veluwe" in the Netherlands, which was hand-planted, tree by tree, to serve as a hunting ground for our Royal family a few centuries ago. It makes me chuckle every time I see our nature preservation corps scream it is nature that needs to be protected. ( I do agree that it needs preserving, I disagree on it being nature)
Both the Black Forest, as well as our National park the Hoge Veluwe are certainly worth walking through though.
EDIT: it is actually a nice combination trip that you can do in 2 days. Untouched nature vs man-made nature. The Veluwe has had a lot of interesting indegeneous and non-indegeneous species introduced to it's eco-system, plus the famous Kröller-Müller museum is situated in the park as well. Here's a link to the park's official site:
https://www.hogeveluwe.nl/en/plan-your-trip/visitors-centre The Veluwe and Black forest are just a few hours driving apart, more so if you take advantage of the not-really-existing speed limit on the german highways
(careful though, even though you are allowed to go about as fast as you want if you keep on the leftmost track of the german highways, you will NOT be insured if you go faster than, I think it is 120 km/h, plus if you do get into an accident at high speed (and manage to survive), you will probably face serious charges against you. Anyone from germany here correct me if this has changed since the last time I was in germany (over 10y ago now). Buddy of mine used to push his pedal to the metal there. I'm not sure if I really liked going 300+ km/h in a vehicle that does not have wings)Frankfurt is really close to the Netherlands too. You could do Blackforest on one day, and Veluwe the next day. It's a nice contrast.
P.S. on the topic of German highways, I believe they recently instituted a toll law. Not sure what that means for tourists, but if you go for a rental car, you might need to prepare for having to pay toll to use certain (or all) highways.