The cruise scene is shifting from oceans to rivers, with more than 2,000 river ships now carrying vacationers on the exotic rivers in Europe.

Statistics show that cruising Europe's rivers is expanding at a much faster rate than its counterpart on oceans.

Leading the flotilla is Viking River Cruises, both with number of ships and innovations.

The latest change is the Viking Longship, expanding the ship's length to 135 meters, the maximum that Europe's river locks can handle.The Longship's length is the equivalent of one-and-a-half football fields, with luxuries to match the expansion. Viking's Longships can accommodate up to 190 passengers. Many of the staterooms now are with balconies.

Viking put 12 of the new Longships in service in 2013, with another 14 coming on line in the spring of 2014.

I was on the final cruise of the 2013 season, Passage to Eastern Europe, which ended in early December.

We spent a week traveling the Danube from Bucharest to Budapest, with sightseeing in Romania, Bulgaria, Serbia, Croatia and Hungary.

There also were pre-cruise and post-cruise stays in both Bucharest and Budapest.

Who takes a trip like this? The passengers were mainly experienced travelers, most of whom were converts from ocean cruising. Our trip had 146 passengers; almost 100 were Americans.

There also were Brits, Canadians and a handful from Malaysia, India, Denmark and Belgium. More than half of the passengers were repeaters who had cruised with Viking before. Following the cruise, the majority rated the trip as an experience that exceeded expectations.

The Viking Aegir concentrated on keeping the repeaters happy. "They know what to expect, and they look for things that represent improvement over their last cruise," said George Sideov, the cruise program director. "Excellent wines have been added to the meals at no additional cost. The same is true for Wi-Fi connections. Clean environment enthusiasts are pleased to discover that 10 percent of the energy now is provided by solar power.

"The typical passenger seems well grounded on what to look for.

They have done their homework on the area, and they're eager to learn more.

Viking port tours are included, yielding a wealth of additional knowledge by local tour guides. These tours are loaded with information and personal anecdotes on life in each of the individual locales. Also, experts come aboard to deliver informative lectures on a whole range of topics," he said. A general description of the average passenger is upper middle class, 60-plus years of age. The group is small enough that by the cruise end, they are friends on a first-name basis. These aren't gambling enthusiasts. There's no casino. There are no big shows. Entertainment comes from cocktail piano music and musicians and dancers who come aboard with ethnic performances when the ship is docked.

Passenger interest centers mainly on the history of the many area sites visited. It's a photographer's dream. The Balkans have seen a century of wars and upheavals. War damage still is visible, and so are signs of remarkable recovery. New construction pays attention to the distinctive local customs and traditions. The shadow of the remains of the Iron Curtain still may be visible throughout the area, but Russian influences now are confined mainly to history books.

Overall, the river cruise is a restful and informative scenic adventure in comfortable luxury.