Wasn't that impressed with Marksburg Castle
"Marksburg Castle is the only hill castle on the Rhine that has never been destroyed. It has been lived in for over 700 years and thus represents an ever-changing and developing building complex that has been growing into its present shape over the centuries."
I found the castle/tour pretty boring. It's relatively small and so, i guess, in my opinion I didn't find it as impressive or interesting as Burg Rhinefels.
Here's the website so you can decide for yourself:
Unique Suggestions: You have to take a tour to view the castle - no wandering off by yourself - so it's definitely more enjoyable if you get a tour in your own language. Unfortuntately this is not guaranteed. We just turned up at the castle and so we were told we could not get an english tour and would have to join a german tour - but then luckily a big group of english people turned up and they organised an english tour for us. May be worth ringing ahead to see if there are english tours organised for the day you want.
Fun Alternatives: I thought Burg Rheinfels in St Goar was better. Although it's half in ruins, it's bigger and more fun to look around.
Learn German before...
We wanted to visit the castle and bought the tickets. Nobody told us it was mandatory to join a group until we got into the castle and someone shouted in German... You can't visit the building on your own but you must follow a group. The only problem was that the guided tour we had to follow was in German... Can you imagine listening for more than 1 hour to a man speaking German and not understaning a word???
Unique Suggestions: Please, ensure you join the right guided tour... At least, in your own language...
Fun Alternatives: There's no other way to see the castle apart from this... :(