While I haven't canoed it, I cycled the whole Danube from the sources of the Brigach and Breg in the Black Forest in Germany to the delta in Romania. AMA.
Do you have recommendations for folks who can only do a shorter trip (say, a long weekend, or a week)?
That being said a few other sections come to mind:
- the very start from Donaueschingen to Regensburg is on beautifully wild cycling paths in the middle of nature with a number of interesting cities along the way
- Vienna - Budapest + train back is another fun loop including 3 capitals!
- For the more adventurous, the Serbian part is very scenic too. Belgrade is great. Leaving it on the busy road not so much. After that you quickly find yourself on a meandering road along the shore with spectacular cliffs and tunnels. No cycling path anymore. But well worth it.
- Romania is still challenging for cyclists, but the delta is very spectacular if you get a chance to visit it (by boat, no bike , as there are no roads).