Rhine River Valley towns

Ten hours is not nearly enough, but if you're there, spend it in St. Goar. The castle ruins there are the best thing on the middle Rhein. Unless you have a lot of time, the boat is too slow. The view is good, but the time spent is too much. Take the train.

You could take the train up one side of the river and back down the other side and then you can get off the train where you like. If you go this route, the easy thing is to take the ferry across the Rhine, rather than switch sides of the river in Koblenz. To pick the best town to stop in depends on what interests you the most. Some people like touring the Marksburg in Braubach, others prefer Burg Rheinfels in St. Goar. Others like the beautiful old churches in Ober-Wesel, St. Goar or Lorch. Still others like taking chair lifts up over the vineyards in Rüdesheim or Assmanshausen, or walking around the walls in the various towns. You may just like sitting on a ship for a couple of hours too. It is a very pleasant way to view the Rhine. Most towns have plenty of wine cellars for a drink or two of the local wines, plus pretty good food. There aren't really any bad choices.

10 hours should be plenty of time to take the boat down to St. Goar. Get off and see Burg Rheinfels. Then train to Heidelburg. You will be very disappointed if you only take the train.

10 hours from when to when? Train to Bingen from FRA: about 1 hour. Cruise from Bingen to St. Goar - 1.5 hours to see the best part. St. Goar: 2 hours for Rheinfels and town. St. Goar to Braubach for Marksburg Castle: a brief ferry ride straight across the river plus a 21-min. train ride to Braubach. Up to Marksburg, tour, back down: figure 2-2.5 hours. That's probably 8 hours or so altogether if things click well. But that depends on when you actually leave FRA. Train from Braubach to Heidelberg: just over 2 hours with the best connections; the 17:23 or 19:23 departures get you there in 2:11.