I have read many pros and cons regarding including Heidelberg on a trip to Germany. The Rick Steves travel guide that I am relying on is absolutely no help as he suggests avoiding the town altogether but I feel that would be a mistake as I will be in the Neckar Valley area and have one day free from about 10:00am to 4:00pm. Since my time is limited I don't want to be wasting time wandering around without any sense of purpose so if any of you could suggest an itinery for the allotted time I would greatly appreciate it.

Well without knowing what your interest are I will give you a few things I like to do in Heidelberg.
1. Take an early cruise up the Nekar river, it usually takes about an hour.
2. Take a walking tour of the Castle. Here they will take you inside the chapel, wine cellar and explain its history. Afterwards you can walk around the castle grounds especially during good weather.
3. Take the tram ride up to the top of the hill next to the castle area, beautiful view from here!
4. Afterward take a stroll over the "Old Bridge", this is a great place to take pictures that include the bridge.
5. Walking back over the bridge take a short stroll down the hauptstrasse (main shopping street) and stop at Cafe Victoria's for awesome desserts and cappucino served in large cofee mugs you can convince the waitress to let you buy. This is a great place for people watching during good weather when you can sit out in the biergarten.
6. Horse and buggy rides can be taken up and down the Hauptstrasse and can take you nearly up to the castle itself, if you catch it at the opposite end ofcourse.
7. There is a church and museum also in this area. all of little side streets have small shops of book stores, antiques, and clothing. I always bring back some coffee beans from there.

If you are driving, I would take the evening and drive to Speyer to dine at the Domhof restaurant, the schnitzel is delicious and plentiful. Sorry if I am rambling on, I truely miss the place.
Have a great time!

Clea

I did #2, 3, 4, and 5 and loved it! If nothing else, do go see the Heidelberg Castle. In the wine cellar, you can buy a commemorative glass and they fill it with wine, which you drink there. Nice!

Oh, please don't skip Heidelberg. The sheer beauty of the town will take your breath away.

Go to the castle. Take the tram up there, then walk down.

Walk the Hauptstrasse - the main street.

Stop and have a caffe and watch the people.

Cross the Alte Brucke (the old bridge) and watch the barges/boats.

Check out the kids hanging around the various statues/fountains in town.

If you're there in the spring or summer, there should be lots of street performers - including some amazing musicians from the local college.

I have to admit - in the 6 years I've been going there, I've never seen a horse and buggy, but...

I lived there for three years and loved it. Rick Steves is 'off' on this one. Heidelberg makes for a wonderful visit. Don't miss it!The suggestions in the above posts are excellent!