I live in Vienna and frequently kayak (not canoe) the Donau. It’s a very fun and adventurous river, and there are lots of little side channels and island (Au) regions that can be explored. In Spring/Summer, it can be a delightful escape from the city, with many lovely little spots to escape to and forget that civilization even exists.

I’ve considered taking it on a longer paddle, for a few days (must of mine are day trips), so this is really a great resource.