Some might argue that, with less than 200 passengers onboard, free wine at meals and included shore excursions, all river cruises are luxurious, compared to their mainstream ocean counterparts.

There are river cruise lines, however, that stand out as being more luxurious than others. These lines include more in the fare, such as specialty restaurants, custom mini-bars and full spirit packages; onshore events in gorgeous palaces or chateaux; exceptional service, sometimes with butlers; and spacious staterooms with posh linens and upscale amenities.

Take a look at the luxury river cruise landscape -- and find the line that's right for you.

Tauck

Who: The river cruising arm of a luxury land tour operator, Tauck goes out of its way to make itineraries seamless.

Luxury Hotel Equivalent: Ritz-Carlton. Tauck's luxury lies in its anticipatory service, the ships' subdued sophistication and the "all-you-need-to-do-is-show-up" inclusions.

What's Included: All alcoholic drinks and spirits; airport transfers to and from the ship; gratuities; all shore excursions in each port; special events, such as dinner in a castle; bikes for passenger use; in-room mini-bar (soda and water); Wi-Fi.

Special Touches: Tauck is so committed to making its trips hassle-free, the guides hand passengers local currency to use in port for lunch.

Crystal River

Who: Long a leader in luxury ocean cruising, Crystal River has branched into Europe's waterways, first with refurbished Crystal Mozart and in 2017 with its first two new-builds.

Luxury Hotel Equivalent: Mandarin Oriental. Crystal River ships are flashy with their luxury, with Japanese toilets, multiple specialty restaurants and "wow factor" excursions.

What's Included: Airport transfers to and from the cruise; all alcoholic and nonalcoholic beverages; gratuities; choice of shore excursions in every port; special events, such as dinner in a castle; GPS guides for independent trips ashore; specialty restaurants; butler service; in-room mini-bar; room service; Wi-Fi.

Special Touches: We're not sure what to cite first. The much-larger-than-usual spa, salon and fitness center? The true open seating with meals cooked a la minute? The excursions to Michelin-starred restaurants? Crystal wants you to feel like you're on the most luxurious ships on the river -- and in many ways, you are.

Uniworld Boutique River Cruise Collection

Who: Part of a vast portfolio of Travel Corporation companies, Uniworld brings over-the-top country house decor to its river ships.

Luxury Hotel Equivalent: Four Seasons. Just as every Four Seasons property is slightly different with lots of local luxe touches, every Uniworld river cruise ship looks unique -- yet all share the same commitment to service.

What's Included: Airport transfers to and from the ship; all alcoholic drinks; gratuities; choice of shore excursions in every port; special events, such as dinner in a castle (mostly on theme cruises); specialty restaurants; butler service (for some cabin categories); room service (for some cabin categories); bikes for passenger use; in-room mini-bar; self-service laundry; Wi-Fi.

Special Touches: Uniworld ships reflect the rivers they sail on with their decor, cuisine and shore excursion choices, making your cruise an immersive experience.

Scenic

Who: Part of one of the largest collections of Australian travel companies, Scenic promotes a refreshing "do it your way" approach to river cruising.

Luxury Hotel Equivalent: Park Hyatt. Modern and cosmopolitan, Scenic ships have a casually luxurious feel with attentive service and ever-evolving shore excursions.

What's Included: Airport transfers to and from the ship; alcoholic drinks; gratuities; choice of shore excursions in each port; special events, such as dinner in a castle; GPS guides for independent trips ashore; specialty restaurants; bikes for passenger use; butler service; in-room mini-bar; room service; Wi-Fi.

Special Touches: Although its onboard restaurants and friendly staff stand out, Scenic excels off the ship, with more active excursions, Scenic Sundowner events and opportunities for independent exploration.