We were on the Cities of Light cruise. We spent 4 extended days in Prague, 8 days on the river with stops in Germany and a short stop in Luxemborg at the American Cemetery and 4 extended days in Paris.The Rhine was not navigable in some places, but Viking handled it very professionally! I strongly recommend that you do extended days in Prague and Paris. It gives you an opportunity to meet people before embarking the ship as well as time to see so many more sies. Viking has representatives at the hotels and offers many excursions. All are wonderful, but make sure to do Prague by Night and Paris by Night. The guides are all very professional and knowledgeable! The cruise director and all employees on the riverboat are great! The meals are very enjoyable! You will not go hungry! You will do lots of walking on the tours, so wear comfortable shoes. Lots of exercise! You will return home happy and exhausted!