Travel to Braubach (Marksburg Castle) from Mainz - Transport Question

Your DB ticket is valid on the VIA trains. It is a private company and that is why the prices are not shown on the DB site. If you use www.rmv.de you will find the prices and schedules for the trains running on both sides of the Rhine.

If all you cruised was Boppard to St. Goar you have missed 90% of the castles on the Rhine. Why such a short trip? Think about going farther. Use your train ticket to get a great discount on your ship ticket.
The ferry going across the Rhine from St. Goarshausen to St. Goar runs every 20 min. Easy to do.

If you are going to be in Mainz, consider taking the train to Bingen and cruising the river the rest of the way, perhaps to Braubach, then train back. Or ride the ship to St. Goar, tour Burg Rhinefels, take the ferry across to St. Goarshausen, then the train to Braubach. Train back to Mainz.

Personally, I thought Burg Rhinefels was a lot more interesting then the Marksburg, plus you can spend hours there. The tour at the Marksburg is over in 45 min. What were you planning on doing there the rest of the day? You cannot wander around in the castle on your own.

First, as Jo said, VIA is a private company running trains on the German Rail tracks as regional trains under the German Rail schedule and tariffs. They have to accept German Rail tickets, regional passes, etc.

RB stands for Regional Bahn, a milk run train that stops at every station (almost a bus). RE stands for Regional Express, a faster regional train because it only stops at major stations. The VIA trains are probably Regional Bahn.

You probably got "no special fares available" because you only entered one traveller on your query, and the single ticket fare (on the right), 20,40€), is less than any special fare. Had you entered 5 passengers, it would have shown 44€ for the special fare, for a Rheinland-Pfalz-Ticket. Because you are no longer going to Cologne, you don't need a QdL-Ticket. The Rheinland-Pfalz_Ticket covers the stretch where you will be traveling and costs less than the QdL-Ticket.

That's right. You need a Rheinland-Pfalz Ticket. Here's what it covers.

"We will have cruised the Rhine, from Boppard to Goar the day before." I assume this is part of the tour package and you don't wish to make any changes.

"We were thinking of going further to St. Goar to see the Burg Rheinfels also but see we would have to cross the river and do not want to rush. Any thoughts on this?"

Here's a plan for you - no rushing around is involved.

Train Mainz (9:03) to St. Goar (10:00.) See Rheinfels, lunch at the adjacent hotel in the "Landgraf" eatery? There are places down in town as well.
Ferry (13:50) to St. Goarshausen; easy walk to station.
Train St. Goarshausen (14:32) to Braubach (14:53) See old town and tour Marksburg. Afternoon meal in the old town at the zum Goldenen Schlüssel?
Train from Braubach (18:24 or 19:08) -Wiesbaden-Mainz (20:08, 20:48.)

You can check your exact date for the above train connections.

Thank you all! Russ, I think we are going to follow your itinerary! Appreciate everyone's help with this!