At the confluence of the Danube, Inn and Ilz rivers, Passau is also situated at a meeting of cultures. The town began as a Roman settlement, enjoying the rising tide of influence as the largest bishopric in the Holy Roman Empire and enduringly vibrant as a hub for various trade pursuits, including salt, swords, and ideas. Wander the cobbled streets of Old Town, gaze upon arched bridges and Italianate manses and visit magnificent St. Stephen’s Cathedral and New Bishop’s Residence.

Named the European Capital of Culture in 2009 and added to the roster of UNESCO Creative Cities as a City of Media Arts in 2014, Linz embraces the present and future, with reverence to its past. The city’s layout reflects its history, with an ancient medieval center encircled by neoclassical, neo-baroque and neo-Renaissance neighborhoods.

Best known for its fortified baroque Benedictine monastery, Melk Abbey, the town of Melk boasts an assortment of smaller gems. Among them, the city’s riverside location, serene and regal with a ribbon of wooded groves giving way to the lovely village. Cobbled lanes and a petite size make for a pleasant stroll with a chance to discover its 16th-century Town Hall, or Rathaus, in the center of town, and Haus am Stein or House at the Rock. Built in the 15th century, the vine-covered abode is Melk’s oldest building.

Continue your adventure cruising the Danube Wachau Valley.

Storybook-beautiful Krems marks the beginning of the Wachau Valley and showcases a true crisscross of old and new. Putting the old and new literally side by side is a preserved length of the old city walls, for instance, while designer shops housed in the regal 18th-century buildings of the Altstadt exist alongside modern department stores. The lower Old Town is an area for pedestrians and cafes, while one of the oldest parish churches in Lower Austria can be found in the upper Old Town.

Once the capital of the Austro-Hungarian Empire and forever known for its manicured gardens, ornate architecture - especially that of the famed Ringstrasse - and distinguished roster of composers who either were born or lived here, Vienna finds itself at the very center of European culture, even as it sits near the border of the Czech Republic, Slovakia and Hungary.

This buzzing capital city is the heartbeat of Slovakia; a historic gem that stirs the imagination. A maze of cobblestone streets winds around 18th-century buildings and a pulsating modern art scene. Explore the museums, cathedrals, and palaces, and relax at a shade-covered sidewalk café. Photography buffs will want to snap images of the medieval castle looming high above the city.

Have a scenic cruise into Budapest.

Commanding both sides of the Danube – with the Chain Bridge connecting hilly Buda with flat Pest – Hungary’s capital enchants with its magnificent architecture of domes and spires, 18th-century homes, bridges, and lampposts. The UNESCO-listed Castle Hill welcomes all to explore Buda Castle, Trinity Square, Matthias Church, and Fisherman's Bastion.

Enjoy your breakfast aboard the Crystal Mahler and disembark at Budapest.