Regensburg's nomination dossier seems to document every single structure in town. This will make great historical material in a few hundred years! ICOMOS however was not amused and complained that it's not about the number of sites but about the themes they represent.
I made good use of the lists of structures from all ages and plotted the most interesting sounding ones on a map of Regensburg. I visited the town on a day trip from Bamberg. A good place to start is the historical museum, which holds a large exhibition on the local Roman history. It shows how the Roman military camp developed into a town. All are very well displayed, although signs are in German only. The entrance fee is 2,20 EUR.
I then checked out two of the most prominent tower-houses, something that I never expected to see here. Most of the buildings here look very new, they have been restored extensively in the 1990s. They all have signs telling their historical value. Some sites I couldn't link to the description in the nomination file however, for example I noticed no wood at all at "the oldest completely preserved wooden building in Germany" (Keplerstrasse 12).
Back on my way to the train station I had a quick look at the Monastery of St. Emmeram. It still has very old frescoes on its facade. In all, I spent about 3.5 hours in town and I had to rush at the end to catch my train.