A great many of the rivers cruises by all companies are, in fact a combination of land and cruise, as you have noted. Cruises from Paris to Prague, for example do not cruise in or out of either city. Many cruise companies also have pre and post cruise extensions of varying lengths. We took a Paris to Normandy cruise with Grand Circle last spring that had a 3 day pre-trip extension in Paris and a 3 day post-trip extension to Brittany. There are also 4 day extensions to London and the Loire valley. For a look at the trip, see my blog/trip report at http://jackthetravelingman-seine.blogspot.com. Grand Circle will also put together a combination of one of their cruises and one of their land tours. River cruising is unlike ocean cruising in that the emphasis is on the ports not the cruising. The best cruises, in my opinion, are those that spend the most time in port. It's just that the traveling time between cities is far more pleasant than on a bus.