From Heidelberg to Rothenberg-Nurnberg-Mannheim-Baden/Baden

I think you might want to clarify your question a bit. You are going to be in Heidelberg from 16 May until 24 Sept. and you want suggestions for a 3 day trip?

I think you mean that you'll be in Heidelberg from May 16-24, Joe. I hope that's right. I already posted something about Baden Baden in the transportation post.

As far as Mannheim goes, there's not a lot of "tourist" things to do there. They have a castle which is now part of their university and a beautiful church which was destroyed in WWII and rebuilt. There's lots of nice parks and walking trails, including a whole series of trails along the Rhine. And there's tons of shopping really close to the train station.

This is more than you can do in 3 nights. If you're rushed don't spend more than one night in Rothenburg. Just be sure to catch the Night Watchman's tour at 8. Rothenburg is 4 hours by train to Baden-Baden (via Steinach, Ansbach, and Karlsruhe). In Baden-Baden the spas are a must. If you can only do one of them then 3 hours at the Caracalla spa would be my preference (bring a bathing suit and a hotel towel). It's less regimented and less expensive than the Freidrichsbad spa. There's also a great restaurant in Baden-Baden called Weinstube Baldreit. It's in Rick's guidebook and definitely worth a try. Spend one or two nights to Baden-baden.

I live in Mannheim and when friends come to visit me from the States I take them to Heidelberg and Rothenburg :) There's not a whole lot to see here. Mannheim is an industrial city that has been almost completely rebuilt since the war. You'll enjoy your other options much more.

Are you taking the train or driving? If you're driving and using a GPS, just a few words of wisdom that I learned the hard way. When you set your GPS for Rothenburg make sure you spell it "bUrg" and not "bErg". Did you know that there are both? It's a pretty drive to Rothenberg with an "e" but not much there when you get there :)

Enjoy your trip!