The Romantic Road runs from Würzburg to Füssen , not to either Frankfurt or Munich and runs for 350 kilometres, it is scenically beautiful but for me the highlights of the Romantic Road are the Residence in Wuerzburg, the walled town of Rothenburg ob der Tauber and Neuschwanstein Palace near Fuessen.
As the road itself isn't romantic, but possibly some of the places it passes through, with a short vacation time just take the much faster autobahn A7 which passes near these three places.
From Würzburg, the Romantic Road briefly passes through the Tauber Valley, which is mostly in the state Baden-Württemberg. Popular stops in this valley include:
Bad Mergentheim with a large Teutonic Order castle and a wonderful Rococo church;
Stuppach with a remarkable Matthias Grünewald painting of the Madonna;
Weikersheim with a splendid Renaissance palace; and
Creglingen with its world-famous Tilman Riemenschneider altar and the Fingerhut (Thimble) Museum.
Rothenburg ob der Tauber
The most popular stop on the Romantic Road and for many the highlight of a visit to Germany is incredibly romantic Rothenburg ob der Tauber. This small town is completely encircled by a town wall and has managed to maintain its late medieval appearance.
The best part of Rothenburg is to wander in its narrow alleys and along the sentries’ walk on the town walls. Most day-trippers – and there are huge numbers of them everyday – depart by late afternoon allowing overnight hotel guests to enjoy some tranquility and a very romantic atmosphere.
The Medieval Crime Museum has excellent exhibits of torture instruments but also a very serious presentation of the medieval justice system. Also worth seeing in Rothenburg is the Holy Blood Alter (Heilig Blut) by Tilman Riemenschneider in the St Jakobs-Kirche. The German Christmas Museum and numerous Christmas decoration shops of Käthe Wohlfahrt scattered through the old town are also popular sights.
The Romantic Road in the Romantic Franconia Region
Several further romantic sights with far fewer tourists follow south of Rothenburg ob der Tauber:
Schillingsfürst has a Spanish Baroque palace;
Feuchtwangen is famous for its 12th-century Romanesque cloisters; and
Dinkelsbühl has romantic alleys and is fully encircled by a town wall.
Then from Fuessen you can head for Interlaken and the Bernese Oberland which is lovely.
There are a lot of other nice places besides Gimmelwald. Basically there are two fairly quick routes, the route mainly through Germany to the Bodensee (Lake Constance) should be shorter and quicker than driving mainly through Austria.
For the autobahns in both Austria and Switzerland you will have to buy a vignette (sticker), an Austrian or Swiss “Vignette” must be displayed on a car’s windshield.
Prices for an Austrian passenger-car vignette range from 7.60 euros ($10) for a 10-day sticker.
Hope my answer has been helfpul!
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Dont forget to check this links of interest:
Fussen Germany The Romantic Road Neuschwanstein Castle