“Attention ladies and gentlemen. We are approaching a very low bridge, and we kindly ask that you vacate the Sun Deck until we have passed.” Floating down Moselle River, Peter Deilmann River Cruises’ Heidelberg is passing under a bridge — a low bridge.

The crew removes not only all tables and deck chairs from the Sun Deck but also the side railings. Even the captain’s pilot house must be lowered so that it is flush with the upper deck.

Welcome to river cruising in Europe, where the experience is unlike any other. With the ability to cruise through the heartland of Europe, river cruises have all the advantages of a bus tour, but without the hassle of having to change hotels or deal with your luggage – or, let’s face it, endure the long bus rides.

River cruises have resonated so well with travelers, in fact, that 2010 will represent a record year for the number of ships offering river cruises.

“River cruising continues to be an in-demand product, as veteran ocean cruisers look for something different,” says Ana Figueroa, director of business development for AMAWaterways. Her company introduces two new ships in 2010.

Joining the parade of ships, Cruise West, a Seattle-based small ship operator, that introduced a new vessel on the Danube River this year. President Dietmar Wertanzl calls his company’s foray into Europe “a natural progression as we continue to provide intimate, up-close experiences not available on larger vessels.”

It’s hard to imagine a more up-close experience. Back on the Moselle, Heidelberg passes under the bridge — with only two inches to spare.

Austria’s third largest city, Linz is a charming town where river cruisers dock alongside the Danube’s banks within walking distance of the city center. Most tourists head for the Hauptplatz, reputed to be Europe’s largest baroque square, where you can take a seat in a cafe to try the famous “Linzer Torte,” a cake comprised of jam and almonds.

On New Year’s Eve, the city celebrated with an opening ceremony commemorating Linz’s role as European Cultural Capital 2009.

Opening ceremony events included an exhibit, Standard Time, where up to 80 workers changed positions of a wooden exhibit each minute to reflect the current time, and the Rocket Symphony, where more than 400 amateur singers complemented with their voices the fireworks over the Danube River.

The year 2009 will see many other events in Linz, including art, movie and culinary festivals throughout the year.

Also, 120 free internet hotspots were installed in Linz, including the entire main square.

In Austria, by the way, the pig symbolizes good luck for the new year. Tables may be decorated with miniature pigs made from marzipan, maple sugar, fudge, cookie dough or chocolate.

People often exchange miniature marzipan, plastic or ceramic pigs as gifts.

Immortalized by Johann Strauss in Blue Danube Waltz, the Danube winds from Germany’s Black Forest through Austria into the Balkans before dumping into the Black Sea.

The romantic river flows through six countries and meanders for nearly 1,800 miles. Some of Europe’s most-fabled cities — Regensburg, Passau, Linz, Vienna, Bratislava, Budapest — are situated on the banks of the Danube, making the Danube a good choice for first-time river cruisers.

On our eight-day cruise on Uniworld’s River Empress, there were both first-timers and repeaters. Our cruise began in Budapest and ended in Passau, with an overnight on board in each city at the beginning and end of the cruise.

Ashore, Uniworld includes at least one free tour in each destination, so that passengers get an overview and introduction to the places they visit. Following is a brief overview of the destinations we visited along the Danube.

Budapest was once referred to as the “Queen of the Danube,” because of the city’s cultural significance at a time when Hungary was three times the size it is today.

On one side of the Danube, hilly Buda retains much of its Middle Age charm; its cobbled streets and Gothic buildings have been well preserved. On the other side of the river, Pest is the thriving city center.

River Empress was docked on the Buda side. A free ferry shuttled us between Buda and Pest.

Bratislava. Slovakia’s capital city was a “capital in exile” for Hungary’s kings and archbishops during Turkey’s occupation of Hungary and most of the middle Danube basin from 1526 to 1784.

Bratislava is dominated by an enormous castle that stands sentinel over the Danube. Though the castle dates back to the 9th century it was razed in 1811 and rebuilt.

Vienna was the next stop for River Empress. After the included city tour, many passengers visited Schonbrunn Palace, the imperial summer palace of the Habsburgs, one of Europe’s principal sovereign dynasties from the 15th to the 20th centuries.

Vienna is characterized by beautiful parks, legendary Viennese coffee houses and Baroque palaces. One of the city’s most famous landmarks, Stephansdom (St. Stephen’s Cathedral) is also one of Europe’s most impressive Gothic structures.

The musically inclined will appreciate that Mozart, Beethoven and Strauss composed their greatest operas and symphonies in Austria’s capital city. The composer Schubert was born here.

An optional excursion offered by Uniworld features an evening concert, and this one is a “don’t miss” for lovers of music and culture.

River Empress called on Durnstein one morning, and Melk (pictured) that afternoon, with scenic river cruising and an outdoor Bavarian buffet on the upper deck.

Using the bicycles on board, a group of us bicycled through the vineyard-rich Wacchau Valley in Durnstein. Read more about that by clicking on “Pedaling Along The Danube.”

In Melk, the included tour took us to the 900-plus-year-old Melk Abby, situated high atop granite cliffs overlooking the Danube and the village of Melk.

From Linz, on the following day, most passengers opted for the included tour to Salzburg (about two hours each way), birthplace of Mozart and the setting for the acclaimed musical, “The Sound of Music.”

Situated at the confluence of three rivers, Passau marked the end of our cruise. We overnighted on board.

The included tour featured a walking tour and an organ concert, performed on Europe’s largest pipe organ at St. Stephan’s Cathedral.

Disembarking passengers either transferred to Munich’s international airport, 90 minutes drive, or for a post-cruise stay in Prague, about three hours by motorcoach.

Our cruise ended in Trier, Germany’s oldest city and an outpost of the Roman Empire as early as the 3rd century BC. Roman ruins are found throughout the city, including an ancient Roman gate.

Dark clouds rolled in on the last day of our seven-night cruise, but spirits remained high on board. As passengers head into Trier, Germany’s oldest city, we conduct a series of exit interviews on our final full day before disembarking.

Heidelberg’s pilot house, where the captain navigated the river vessel, raised and lowered to pass under low-lying bridges. In this scene, you can see the pilot house rising after passing under a low bridge on the Moselle River.

One of the more charming ports of call during our seven-night cruise was on the Moselle River. Heidelberg docked within a 5-minute walk from the city center of Bernkastel and within a 20-minute walk (with a moderate grade) to the castle ruin of Burg-Landshut that overlooks the city. The community’s wine-growers tend Germany’s largest continuous expanse of vineyards. Needless to say, the wines here are heavenly.