From Koblenz, we visited Burg Eltz.
It was a beautiful castle nestled in green and the drive there was great! very scenic and serene.
The website said that from the car park, it was a comfortable 800m walk to the castle -- yup, the way DOWN there was comfortable. But walking up wasn't that comfortable with a toddler in a stroller! but it was definitely a short distance and much better compared to the uphill path to Marienburg Fortress in Wurzburg! ha. took us less than 10 minutes to make our way uphill.
There was a shuttle bus service, so if one doesn't want to walk up the slope, there's an alternative ;) but taking the shuttle bus will mean that we will miss the "photo view point" which gave excellent shots of the castle :)