In comparison with the giant cruises ships of the Caribbean which are party havens, the smaller river cruises through Europe tend to be quiet and relaxing. Some of the benefits include the small size of the ships which means there are not thousands of people embarking and disembarking at each port making for a much quieter, more relaxing experience.
The areas with these cruises available range from the Danube, Rhone and Rhine to the coast of Croatia and the rivers of Russia. Depending on what you are interested in seeing and which cities and towns you are interested in visiting there are certainly plenty of options.
The small ships hold around 100 passengers who skew into an older age range of 50+. Although the ships are small, they do often many amenities. This includes nightly entertainment, fitness centers and hairdressers; this all depends on the cruise line and the particular ship. One of the biggest draws for these cruises is the food. Typically the restaurants aboard will feature specialties from the region that you are cruising through so you are not missing out on being unable to head into the restaurants of each city.
Cruises can be purchased from standard travel agents and many are able to secure deals that also include some or all of the available shore excursions which can significantly increase the cost of being aboard the ship. However, this needs to be balanced with how much it would cost you for transportation between these cities as well as hotels, guides, food and all of the rest.