Considering the Avia Hotel (Gunther Schwecke.) in Regensburg?
A VT member wrote the following comment about visiting Regensburg:
Visit BMW by bilgeez
The BMW factory in Regensburg gave tours there on certain days of the week. They may still, it was very interesting. The tour guide spoke excellent English. The plant is south of the city in an industrial area. City buses do go there, but one has to pay the extra fare for a "Fernfahrt" as it is away from the city.
Check BMW's website to see if they have tour info. If I find any better info in my "archives" I will add it in here.