Originally Posted by Spent_All_My_Miles
Heidelberg is nice.
Frankfurt does have a few museums of interest should you have some free time on the days of your meetings.
I'd second this option, though you have been there many more times than I have. One particular restaurant comes to mind for German food; the Golden Sheep/Ram? Sorry, I don't speak German so don't know that actual translation for it. I thought it was very good, and seemed relatively authentic German fare.