After tracking the Danube river from Passau to Vienna in 2012, and Vienna to Budapest in 2015, we covered the remaining, close-to-home part between the origin of the Danube river in Donaueschingen all the way to Passau. Planned to take 10 days, we rode the whole 600 kilometers in 8 days, and travelled back by train the same day we arrived in Passau. Again, rather flat but hilly (even steep) in some places, and in a way, more of the same. So though the whole route has been tracked and photographed, the number of images is less than normal.
The data can be found here