Rhine and Rothenburg

Go to the German Rail website for rail schedules all over Europe. Put in from: a town on the Rhein (St. Goar?) and to: Rothenburg od der Tauber. You'll get the schedules for most of train connections between the towns. That query will tend to "favor" the faster, express trains, which cost more. Click on "only local transport" to see the least expensive (and slower) regional train connections. You might have to click on "change other data" if the input field has "collapsed" and hidden Modes of Transport.

You can ride the ICE fast train from Paris to either Cologne or Frankfurt, and then go either up or down the Rhine on the slower Regional trains to your town of choice. Get the tickets ahead of time and they will be fairly cheap. The ICE does Paris to Frankfurt in less than 4 hours, so a nice, relaxing trip.

There should be no problem with this itinerary. I would only suggest adding some time for the Mosel River and for Franconia - the larger places near Rothenburg that include Würzburg, Bamberg, and Nuremberg. If your choice of Rhine town is based only on the fewest number of connectioins, you will probably end up in Koblenz or Mainz - both of which are large cities and neither of which are good towns to stay in if you want to enjoy the Rhine. These larger places are good alternatives in winter when the villages are Deadsville, but in summer I would take St. Goar, Bopppard, Oberwesel, or Bacharach over Koblenz anytime, even if an extra train connection is involved.

Those cheap prices Jo mentions are Europa-Spezial tickets, which can be ordered online using the German Rail website. These ticket require advance purchase (at least 3 days, max 92 days); early purchase is recommended because when the lowest priced tickets (€39/p) sell out, the price goes up. These tickets are train specific for the express (ICE/IC/EC) portion and non-refundable as of the day of travel. You can't go through Koeln because that route uses Thalys, and the discount prices don't apply. The fastest routes with the discounted fare go through Saarbruecken (maybe Kaiserslautern), not Frankfurt, but that will show up when you find connections on the Bahn website. It looks like the best you can do is 2 train changes, in Saarbruecken and Koblenz or in Kaiserlautern and Bingen, depending on your final destination. You can purchase similar discounted tickets, called "Sparpreis" for anywhere on the Rhein to Rothenburg odT from the Bahn website for as low as €29 or one person, €49 for two. To get that fare, one connection has to be a train specific, non-refundable leg by express train. These connections take about 4½ hrs through Wuerzburg. You could also go from the Rhein to Rothenburg by regional train. This would take about an hour longer, but you would not need non-refundable tickets to save money. On a weekend day, you could do the trip by regional train by using a €39 Schönes Wochenende (Happy Weekend) pass for hop on/off travel on regional trains anywhere in Germany. On a weekday, you can get the Quer durchs Land ticket, for the same kind of travel, for €42 for two people.

There are trains running on both sides of the Rhein so any of the riverside towns (Boppard, St. Goar, Oberwesel, Bacharach, Braubach, etc) will have good connections. Most of the attractions (Rheinfels castle, Bacharach) seem to be on the left bank, so that's probably the best side to stay on. However, my favorite castle in the area, because it was never distroyed and is not lived in, is the Marksburg, in Braubach, on the right bank. There are a few ferry crossings, the best of which is St. Goar to St. Goarshausen. Of the towns, I would prefer St. Goar. It seems to have the best choice of accommodations and most accommodations are convenient, a short walk down the hill from the Bahnhof. Note: I recommend St. Goar although in 2004 I spent 5 nights in Boppard. I enjoyed a Privatzimmer for €25/nt, but the hosts only spoke German, which might be a problem, so I won't recommend it.