I've lived for one year near at Heidelberg, so I had the chance to see it in different seasons. Finally I have to say it is one of the most beutiful places in germany, to make holidays, and to life as well. It has good infrastructure and you can go from the historic city to the nature in a short time, everything is near there.
Another Place I've spent much time for work was Mannheim, see the pictures below, it is difficult but has nice places as well.
(The picture above is not the reality! Its a photoshop edit.)
The Rhein-Neckar Kreis has many nice places you can visit, the pictures below shows Weinheim, Dossenheim, Schwetzingen and some other spots I've visited in my year there.
The pictures below are from Ladenburg
Now you see some impressions from weinheim
Pictures from my home, Dossenheim:
