Castle day trip from Cologne.

On the Rhine, I would say Marksburg is probably the star attraction. Most of the remainder of the castles on the Rhine are partial ruins. Rheinfels is a little more interesting than the other ruins, mainly because it's pretty big. But within a few hours of Cologne, my absolute preferences would be Wartburg in Eisenach, and Schloß Montabaur.

Thanks Tom.

I would agree with the Marksburg (only undestroyed castle on the Rhein) and Rheinfels (ruins but huge). But I don't know of any tour, and I wouldn't take on if I knew of it. Why pay someone a lot of money to do what you can do yourselves. Round trip tickets from Köln to the Mittelrhein would cost €51,80 for all four of you, €12,95 each. That's €21,80 for all 4 of you with a 5 person Preisstufe 4 Tagesticket to Bonn. It would also cover your trip from Bonn back to Köln in the evening. You can buy this from a ticket counter in Köln Hbf. Also €30 for a Rheinland-Pfalz-Ticket for 4, which would cover you from Bonn into the state of Rheinland-Pfalz and everywhere for the day on the mittelRhein. Get the RL-P-Ticket from a vending machine or for €2 more from a ticket counter. These tickets restrict you to regional trains (no express), but from Koblenz up (So.) the Rhein, that's about all there is. Take a Regional Express (RE) from Köln Hbf to Koblenz, then a Regional Bahn (MRB) to St. Goar. See Rheinfels. After Rheinfels, if you feel like a boat ride, take the KD boat (fare extra, but you should get a discount with your rail tickets) to Braubach and the Marksburg. Or, to save money, take the ferry across the Rhein to St. Goarshausen and the train to Braubach.

Lee,
Great info, thanks. (I wouldn't expect anything less from a Colorado resident - I'm a CU Grad myself) We're pretty travel savy so I think we'll give your train recommendations a shot.