The Altmuehltal is a forested region of Bavaria that surrounds the Danube river upstream of Regensburg as well as the Altmuhltal valley between Nurnberg and Ingolstadt. We toured it more or less by chance having started up the Danube (Donau in German) from Regensburg. The first notable town on this route is Kelheim, mostly because of the impressive museum on the hill above town. Not far from there is the village of Essing pictured here.
Essing is so picturesque that we were forced to stop here for a while and build up a large repository of swan images. There isn't a whole lot to see in Essing (although there is a brewery) but it's a pleasant place to wander around for an hour or two.
Further upstream is the photogenic castle at Prunn which we have failed to take a picture of, so we'll just skip ahead to Reidenburg. It looked like this in a painting found in the Residenz at Munich. This would've been sometime in the 19th century most likely.
Now it looks like this. Not really much different. Along with the ruined castle here (top left) there is another ruined castle on a hill off to the right and the new replacement castle which looks more like a large hotel. Much like Essing there's not a whole lot to do in Reidenburg besides driving very very slowly. In fact, Reidenburg aims to keep tourists by having extremely low speed limits. There is also a brewery just a bit up the Danube from the town center.
There is a long and well-maintained series of biking and hiking trails through the Altmuhltal. The nicely paved bike trails generally run right alongside the rivers and periodically cross small towns. In between towns there is actual forest, although much of it is in smallish clumps surrounded by farmland.
Once you're actually out in the forest proper though it has that Brothers Grimm sort of feel to it. When we visited it was all extremely still. We could hear birdsong but there was not any apparent movement at ground level. A thick layer of mosses and ferns makes for nice hiking.
This path is in a small subsection called Koeschinger Forest. Trails run everywhere but signage is sporadic at best. Presumably there are guidebooks for such things. We spent a while just wandering about in the area before taking our rental car back to Munich and going into the city by train.