my friends have about 10 hrs. at the frankfurt airport in March.
I suggest taxi or train to the Innenstadt, Romerberg, KaiserDom and other sights close by.
Should they take a tour - guided tour- to wine country ?, and how do we arrange that ?
Thanks.
Here's something you might try. Go over to Tips & Trip Reports. Then to Trip Reports. Then to Most intereting Cemetaries in Europe. Go down to Ms. Jo whose entry is about baby cemetaries. Give her a private message and see if she can help.
Have a look a this useful post on Trip Advisor about how to do a layover in Frankfurt:
http://www.tripadvisor.ca/ShowTopic-g187337-i301-k6809373-Layovers_in_Frankfurt_how_to_and_what_to_see-Frankfurt_Hesse.html
(as an FYI, this post was written several years ago and the price of the train tickets has increased. You will want a group day ticket which costs 15.80 € now)
If you only have 10 hours, I don't think you have enough time to get up to the wine regions on the Rhine. Besides, in March, it isn't very green yet. Go to one of the Farmers markets in Frankfurt instead where Riesling is the drink of choice as well as Applewine. What day will you be there? There is a outdoors Farmers market every day except for Sundays and Mondays. On Mondays, you could go to the Klein Markt Halle and their Wine Bar.