Viking was highly recommended by friends, and a river cruise you get to see many different towns near the river, and the tour guides tell you the history of each stop.
The nice thing about a river cruise is that you have not only the hotel, all the meals, and the tour guides for each port.
Relaxing, it was not, because each morning you were up early, first to get your breakfast, then to get ready for your guided tour, most tours started at 9am. Then after the tour, back to the ship for lunch. Sometimes the were tours in the afternoon right after lunch. Some tours ended up quite late, so the dinner was a late one. We saw a lot, however, despite the busy schedule.