If you book extra days with Viking before or after a cruise tour, you will pay a large fee PER PERSON. This is for hotel room and your airport transfer to/from hotel.
Most will find that arranging independent transfer (taxi/Uber/Metro) and hotel will be less expensive. Just need to be sure to know the hotel that is included with your cruise tour, or be willing to stay at a different hotel.
We recently returned from the Portugal River of Gold cruise tour.
We booked economy travel with Viking Airplus, and paid extra fee to select our own flights. United changed the schedule several tim