Interest in European River Cruises Soars IN Europe, where waterways were the roadways of the pre-automobile past, major cities from Amsterdam to Vienna reside on rivers. Centuries after those rivers were supplanted by railways and highways as main thoroughfares, there is renewed interest in traveling on them: at least 11 new river cruise ships are launching this year, and a similar number is expected next year. Over the last five years, many lines have doubled their capacity. "It's all about the destination," said Rick Kaplan, president of Premier River Cruises, an agency in Los Angeles. River cruising is geared to more experienced travelers who want to explore a destination in depth. The focus on attractions beyond the ship is no accident. Because river locks and bridges predate outsize cruise vessels, ships making their way through Europe are comparatively small and short, with limited space for amenities. Instead, they focus on convenience, often docking directly downtown, rather than anchoring at an ocean port that may require a bus transfer. Several itineraries feature overnight port calls, making them a viable alternative to exploring Europe by train or car. Leading the surge in Europe is Viking River Cruises (vikingrivercruises.com). It launched four new ships in March and is adding two this summer, bringing its fleet to 30. According to Torstein Hagen, Viking's chairman and chief executive, the company has grown 30 to 35 percent annually in recent years. "The tipping point is finally here," Mr. Hagen said of river cruises, adding that the company is getting six more ships next year. Our problem is not having enough capacity to meet demand. The new ships - Viking Odin, Viking Idun, Viking Njord and Viking Freya - hold 190 passengers each and have several two-room suites, terraces with retractable glass walls for al fresco dining, and organic herb gardens on the roofs. Many departures are sold out this summer, but cabins start at $1,756 per person for eight-day fall and winter sailings on the Danube aboard the Viking Odin (Budapest to Nuremberg) or Freya (Amsterdam to Budapest). In May, Avalon Waterways (avalonwaterways.com) launched two new European ships, the 166-passenger Vista and the 128-passenger Visionary. Both feature suite staterooms with 10-by-7-foot windows that open to the balcony, top-deck whirlpools, outdoor dining and beauty salons. But it's not about the ship. The Visionary plies the Rhine River between Amsterdam and Basel or Zurich with eight-day trips starting at $2,289 per person, double occupancy, and the Vista cruises the Danube from Prague, where it stays overnight, before another overnight stop in Vienna and ending in Budapest. Eleven-day sailings start at $2,499. The line has announced two more all-suite ships for 2013. Also in May, AmaWaterways (amawaterways.com) christened its 164-passenger AmaCerto with features including two balconies in most guest rooms and a pool with a swim-up bar. The new ship will spend much of the summer on the Danube. Twelve-day sailings between Budapest and Munich, with overnight stays in Vienna as well as starting and ending ports, begin at $2,799. The company plans another European launch in 2013. There are other rivers to explore. The high-end line Uniworld (uniworld.com) announced that it would become the first United States operator to cruise the Po River in Italy, moving the line's 134-passenger River Countess to Venice next April for eight-day round trips with excursions to Bologna and Verona starting at $2,899. Next year it will also replace its Douro River ship in Portugal, which stops in Porto and the wine-growing town of Pinhão, with the 118-passenger Queen Isabel. Several Uniworld sailings are designated multigenerational, but river cruisers tend to be older than ocean liners - the target demographic begins around 50 - and programming hews to history and culture. "I like to say ocean cruising is a drinking man's cruise," said Mr. Hagen of Viking. River cruising is a thinking man's cruise.