Germany and Austria driving vacation

Mimi, that sounds like a great trip. Bacharach and St. Goar are just a few miles apart so I am assuming that you are staying at one or the other, not both. I actually love staying at St. Goar even though most people will say it's boring. St. Goar is easy to reach from the airport so you wouldn't actually need to stay a night in Frankfurt on your way out. Two days and you could see most of that section of the Rhine. Even though I didn't care for Rothenburg, it is a nice stop instead of driving all the way to Munich. I would spend at least 3 days in Munich and 2 in Salzburg. You could drive all the way from Salzburg to Frankfurt on you last full day and catch your flight out in the morning. I did that once, and had the entire afternoon in Frankfurt. Does the 10 days include flight days or is that all in country?

Little towns like St. Goar or Bacharach are easily seen in a couple of hours, and you can actually travel up and down the entire Rhine from Bingen to Koblenz in a day, seeing about 40 castles and dozens of quaint towns. There are also lots of towns similar to Rothenburg, so if sharing a town with 1000's of other tourists puts you off, consider stopping somewhere else. Bavaria is a huge state, so you will have to narrow down your choices to some towns or cities. Salzburg is an easy trip from Munich. My suggestion is to pick two or three bases and day trip from those. Frankfurt or Mainz, Munich, and then Salzburg. From Frankfurt, you can do the whole Rhein, Wuerzburg, Heidelberg, Buedingen, Idstein, Bad Homburg, and Mainz without having to pack up and move each day.

You only have 10 days. Besides spending so much time on the road driving to and back from Munich and Salzburg, you will be missing out on a lot of great places that are easier to reach. Instead of going with the greatest hits, why not draw a 100-mile circle, maybe a little more, around Frankfurt on a map and explore places within that loop. If you avoid driving so much at a time, you can spend more time enjoying the Rhine, going up to Cologne and then cut through to Berg Eltz and the Mosel by way of Maria Laach Abbey. Or, you might drop one or two of the above to add Heidelberg and then visit Schwäbish Hall and Rothenburg, Würzburg, maybe even Bamberg, before working your way back to Frankfurt. There's also a northern route through the Taunus Mountains to the castle town of Marburg; or, to the northeast, beyond Cologne, there's Charlemagne's capital of Aachen and Monschau, which is a rival to Rothenburg as a medieval village. That's more than I meant to say, but you did ask.

I'd probably go with three nights on the Rhine - remember your first day is just to get your feet on the ground and deal with jet lag. My favorites here are walking around Bacharach, exploring Rheinfels in St. Goar, tour Marksburg Castle in Braubach, take a KD line ferry for the roughly 45min to one hour ride from Bacharach to St. Goar (take a local train, 1 per hour, back to your starting point about ten minute ride). From here go to Romantic Road/Bavaria. Wurtzburg is one of my favorites - it has the most sights on the Romantic Road. Rothenburg's nightwatchman's tour and wall/towers make it an excellent stop for a night. Other nice little towns include Nordlingen and Dinkelsbuhl. We opted to use the Autobahn, rather than stay on the slower Romantic Road, and just stop at the places we wanted to visit.

If you check out some of the sights in Bavaria - Neuschwanstein, Wieskirche, Andechs Monestary/Brewery, Berchtesgaden - you will need to plan another night in the area. From here go to Salzburg (you can lose the car before you leave Germany, you won't need it for Salzburg, Munich or back to Frankfurt). Salzburg is one of the most beautiful cities anywhere. Everything is walkable. Plan two nights here, with one very full day of walking around the center, gardens, churches, castle and monestary. After Salzburg, Munich, spend as much time as you can here. Marienburg Platz, the city hall, Frauenkirche, English gardens, Nymphenburg Palace are all great sights. I love the art museums here, but you probably only have time to see them as a backup for a rained out outdoor day. In summary, 3 nights on the Rhine, 2 in Bavaria/Romantic Road, 2 in Salzburg, and 3 more in Munich. If you need to lose some take one from the Rhine (you can do a lot here in one full day, but it's tough when it's your first day) or one from Munich (reducing your stay to one very full day). You can drive back to Frankfurt quickly as long as you don't get stuck in traffic. I like using the train because you're more certain of getting there without delay and can go straight into the airport without turning in your car.