You'll have time for a stopover. I would see Heidelberg as an old city + castle destination. To tour the castle (ruins) won't take that long. There is actually not much to see inside.

…heidelberg.de/Altstadt-Information/english/…

schloss-heidelberg.de/fm/37/Anfahrtsskizze_S…

parking map

schloss-heidelberg.de/fm/37/Plan_Schlosspark…

Parking is however not as easy as it may look on the first sight. There are plenty of pedestrian zones and one way roads. If you can find the way to any of the shown parking places on the first attempt you're good.

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There are a few hundred castles on the route between Cologne and Rothenburg. While Heidelberg as such is worth a stopover - if you're in first place interested in an authentic medieval castle there are better options. E.g. Eltz Castle

http://www.burg-eltz.de/

I agree (as usual) with abalada. HD is as much a lovely town, great views and walks along the river, student sections, etc. The castle (ruins) is largely of the Baroque and not the "medieval" castle most common in Germany. One of the attractions is the large courtyard, small gardens, and views from the castle rather than the castle only. The castle makes sense in the context of the whole town, red roofed buildings, churches, Odenwald forest, etc. Give yourself at least a half-day.

Hi, Last time I went to Heidelberg I went to the castle and it was amazing. The only problem is finding parking anywhere that's close. The streets there are kind of windy and that coupled with a one way system can be pretty confusing.I would plan your route before you get there.

When you get to the castle depending on how much time you have, you can either take a full guided tour, you can even get a hand held translator, or you can simply just look around and enjoy the beautiful view.

I hope you get a chance to make it.

Any suggestions on where to park? Are there any parking lots at all?

There is an underground parking garage at the bottom of the funicular to the castle. May be more prudent parking there instead of looking for a parking spot in abusy city.

As others have mentioned, yes, you'll have time to tour the castle. Have fun in Heidelberg, it's truly beautiful.

Personally, I would visit medieval walled fortified (Gross)comburg Monastery (in www.schloesser-magazin.de/en ) by Schwaebisch Hall ( www.schwaebischhall.de ) between Heidelberg and Rothenburg, an excellent medieval town in its own right. It is unique, actually a large medieval monastery and church within a large medieval castle.

As mentioned before, there isn't that much to see within the Heidelberg palace, unless you want to stand atop the world's largest wine barrel.

Heidelberg castle is more than just "things to see." and a lot more than a wine barrel, Markopolko. That's a cliche. Its in a beautiful setting, especially nice on a summer evening. The grounds are great with excellent plantings. Great views of Neckar River. Lovely courtyard with multiple castle wings, architecture, etc. Since it is a baroque rather than medieval castle it has lovely ornate facade that were designed to be intricate. There is a lovely gourmet restaurant inside with views of the courtyard. When you are there, look around. Much of the beauty is in details.

Heidelberg castle is an icon and very intriguing. It has a great atmosphere and significant history.

Its esp. terrific in the summer, when there are outdoors music concerts (esp. of Heidelberg City Orchestra, very famous), shows on "The Student Prince" (some sung and acted in English), regular fireworks shows, outdoor restaurants and cafes, etc. Don't miss it.