I would love to surprise my husband for his birthday with a nice castle visit along the Rhein. Originally I wanted to take advantage of K-D's free birthday ticket since he loves scenic boat rides, but schedules between the train and boat isn't working out.

The big dilemma is that we have limited time since this will be a day trip from Bruxelles (I know too far), and I think the last short train back from Koblenz is 6pm or Koln at 7pm.

Any suggestions to make a birthday in Germany for a day memorable?

Not sure if I understand your schedule, but if you are looking for a nice castle visit, you should consider Burg Eltz.....which is on the Mosel River but not far from the Rhine. (near the town of Cochem).
You will probably find many postings for that castle, as it is often thought of as the best of the German castles to see.

ttt

We really like St. Goar, a picturesque town along the Rhein. Overlooking the town are the ruins of Burg Rheinfels, which are massive and are really a lot of fun to explore. Bring a flashlight and you can even go into the underground tunnels (if you like that sort of thing..).

There's also a nice view of more castles on the other side of the river, a cute little shopping street, and a few good restaurants. I think that you can also take the ferry across the river to St. Goarshausen, too, but we've never done that.

Good luck and have fun!

Has anyone seen the Marksburg castle? Is it worth it as a day trip from Bruxelles?