Hi,
I'm preparing the next session, which will take place in the Black Forest in the Rhine Tribunal. In Guardians of the Forests, the Black Forest Road is mentioned, and I thought I'd do some more historical research on this. But I can find any mention of it (my search-fu is not strong enough, it seems). Is this road based on historical research, or is it made up by the authors of Guardians of the Forests? 
Cheers,
Eirik
The history is correct, yes - there was a real Roman road following the route described, although the bit about the Mercurian priests was of course speculative. 
I don't think I ever found out a name for the road, though, if it even had one. As a starting place for research, try
en.wikipedia.org/wiki/Agri_Decumates (the name of the Roman province containing the Black Forest)
de.wikipedia.org/wiki/Gnaeus_Pin ... us_Clemens (Roman governor responsible for this and other roads in the province)
A Google image search for "Agri Decumates" yields a few maps, for example
members.tripod.com/~Linus_Gemvik/decumates.html
where you can see the route of the road.
Having been along part of the route many times (the western half is the same as the route of the Schwarzwaldbahn - Black Forest Railway - which is where the train line from Constance to anywhere useful in Germany goes) it's worth stressing just how tortuous the terrain is, which is why the road has to follow the River Kinzig for so long. It looks like a maze of winding valleys blocked by ridiculously steep hills. From the Rhine valley in the west to (say) St. Georgen is an increase in altitude from 150 to 800m, although I'm guessing the road has a lower route than the railway in the east.
Dug out a bit more info from Wikipedia:
en.wikipedia.org/wiki/Kinzig_(Rhine#Infrastructure
The (modern) German name for the road is "Kinzigtalstrasse" ("Kinzig valley road"). Here
rolf-pfefferle.net/teilstr_roem.html
is a map of a small part of it. The author says that he discovered some remains of the Roman road in 2003. Interestingly, here the road is not immediately adjacent to the river but maybe a hundred metres or so up the valley. Thus I imagine that on one side of the road there would be a precipitous drop, making things potentially nasty for PCs... 