We will be staying with friends in Heidelberg for a few days in September. While we are there, we would like to take a day trip to Trier, driving from Heidelberg. Is it realistic to think we can see the highlights of Trier in one day? It takes at least 2 hours to drive from Heidelberg, so I can see this will make for a long day.

Trier can keep you occupied for longer than that = but in one day you can see the Porta Nigra (huge Roman arch) as well as the extensive museum of Roman remains (some beautiful mosaics and a host of other ruins and displays), visit the church and also see some of the cute Germanic parts of the town.

One of the things we liked is that although there are obviously a number of tourists - there are also many locals - it's not as inundated with tours/tourists as is Heidelberg, etc.

Thanks for your reply. Yes, unfortunately we don't have as much time as we'd like, but we are hoping one day is better than not seeing Trier at all. Might be our only chance to get there.

You can definitely get a nice feel for Trier in 4 or 5 hours.
Of course, you'll see the Porta Nigra, take lunch at one of the outdoor cafes on the square, walk to the Ampitheatre and the Baths.
More info on sights at

http://www.trier-info.de/english/indexths!

Thank you for this very helpful link!