Need urgent quick suggestions! Overnight trips near Frankfurt

I would go over to Büdingen as they are having a really large Medieval Fest from 8-10 July. The town itself is worth a visit any time of the year, but this fest is only held every 2 years. With 200 stands this is the largest one I have seen around here. Büdingen is a walled town, with their original walls from the 1300's and 1400's. It has never been bombed or burned down. The Fachwerk houses inside the town are some of the best examples I have seen. Add to this an unusual 13 sided palace, and you have one on the best kept secrets of this part of Germany. The whole town is taking part in this fest, closing off all the streets to cars and traffic and dressing in period outfits. It is only an hours drive out of Frankfurt. Near-by, you could also visit Glauburg, and the Celtic exhibits there. These are both located in the Vogelsburg mountains. For more nature, go up in the Taunus mountains north of Frankfurt. Visit the Saalburg, near Bad Homburg, or Idstein, or Kronburg, or Eppstein. South of Frankfurt is the Odenwald, and here you can visit Heidelberg. Wurzburg is near and so is Aschaffenburg, Seligenstadt, and Darmstadt.

If nature is what your looking for, you have some good options nearby. To the south, you will find the Odenwald, which is a low, forrested mountain range criss-crossed with hiking trails. Much like the Black Forest with more forest and far less tourism. To the north of Frankfurt lies the Taunus mountains, of which I am less familiar, and to the southwest on the other side of the Rhine is the Pfalzerwald, which is probably the most wild, undeveloped region of Germany. For some hiking ideas, book stores in Frankfurt should sell guidebooks and maps of all three areas. In the Odenwald, probably the most interesting hikes I have taken include ascents to the summits of the two highest points in the region, Katzenbuckel and Neunkircher Höhe. Each of these has a tower on top that allows you a great view of the surrounding area. Another good hike is up to the top of the Heiligenberg, the mountain on the opposite bank of Neckar river from the Heidelberg Schloß. Besides some great views of the old town, there's the ruins of an old monastery on top, and just below this, one of the largest, intact building projects of the Nazi era, the Heidelberger Thingspiel. Mannheim has grown on me, but the only thing I would recommend here to a visitor is the wonderful Luisenpark, which I would rank as one of the most beautiful urban parks in Europe. Worms has the old cathedral, the Niebelung bridge over the Rhine, and not much else of interest.

DEFINITELY cross the French border to Alsace! It's 2-3 hours from Frankfurt and you'll have a TON of options to choose from based on your interests: city (i.e. Strasburg) or wine town, history, food/wine, hiking (the Vosges Mountains are fab), and TONS more. Great tourist infrastructure, but at the same time, it's not swarming with American tour groups (i.e. you still get a taste of the local culture without having to search for it).