Check out the Danube. It's pretty scenic, and there are good bike trails along long sections of the river. I've done a bike trip on those trails, but I don't know how easy it is to kayak the river. The Danube contains a number of dams with locks. I don't know how hard it would be to portage around the locks with or without a kayak cart, or to float through the locks with other river traffic. Because large numbers of people bike the trails, most hotels along the river have bike storage rooms. However, getting a sixteen foot long Adventure into some of those rooms would be an adventure.
I've done many multi-day unsupported wilderness whitewater river trips, including a lot in the 1-2 week range, but haven't done any multi-day urban kayak trips. It seems to me that since you may end up staying in lodging a couple of blocks from the river or shore, and on some rivers you'll need to portage around dams or locks, you'll probably want to bring a center-mounted kayak cart so you can move your loaded kayak and all your gear in one trip. Leaving part of your gear on the shore while you make multiple trips invites theft. You'll be able to carry about twice as much gear in your Adventure as most unsupported bicycle tourists carry on their bikes, but it'll be easier to get your loaded kayak on a cart and haul it up hills if you you restrict your gear to the amount you usually take on bike trips.