Viking, well yes, they have great advertisements, and gorgeous photos of the new 'longboats', however here are the facts.
1). They must have your whole entire cruise fee payable immediately payable upon booking.
2). Watch out, depending upon where your cruise goes, look at the following : River swelling, lock strikes, time of year for river swelling ( and/or depleting) etc. ALL of those affect your cruise.
Well, we had a lovely cabin , however, we were only able to sit on it for one time. Viking does not tell you that while, in dock, that other Viking boats can " Dock up" next to your boat, and thereby obliterate your view of anything, except the boat next to you. This happened to us 5 out of 8 cruise days.....