Gene Sloan

USA TODAY

SOUTHAMPTON, England — It was a big day Sunday for cruise fans as Royal Caribbean's record-breaking Harmony of the Seas set sail with paying passengers for the first time.

At 226,963 tons, Harmony is the largest cruise ship ever, a floating mega-resort with three main pool areas, a water slide complex, an adults-only solarium, an ice skating rink, two rock climbing walls, a basketball court and a mall-like indoor promenade with shops, bars and eateries. It departed from Southampton, England on a four-night voyage to Rotterdam, The Netherlands.

Harmony is a larger version of Royal Caribbean's giant Oasis of the Seas and Allure of the Seas, the previous size leaders in the cruise world. While a number of its features are the same as its siblings, it also offers a number of new additions. Among them: Ultimate Abyss, which just might be the most thrilling attraction ever conceived for a cruise ship. Comprised of two swirling slides, it drops 10 stories from near the top of the vessel down to one of its lowest decks.

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Harmony also is home to a Bionic Bar where the drinks are served by robot bartenders -- a concept that first debuted in 2014 on Royal Caribbean's Quantum of the Seas. In addition, Harmony has larger cabins than Oasis and Allure in some categories, and windowless "inside" cabins are outfitted with Royal Caribbean's exclusive Virtual Balconies, which offer a real-time view of the outdoors. It's a concept that first debuted in 2014 on the line's Navigator of the Seas.

The water slide area on Harmony is something Royal Caribbean just began adding to ships this year.

Like Oasis and Allure, Harmony also has an open-air, tree-lined area called Central Park with restaurants, bars and upscale shops such as Bulgari. The vessel also has a 1,380-seat theater that will show the Broadway musical Grease, comedy club, jazz club, casino, aquatheater and karaoke bar. It has more than a dozen eateries including an Italian restaurant by celebrity chef Jamie Oliver.

Wider than Oasis and Allure by about 2.5 feet and a tad longer, too, Harmony holds nearly 100 more passengers than its sisters at double occupancy. Its total capacity is 6,780 people, not including crew -- a new record for the cruise industry.

After an initial series of cruises in Europe, Harmony will re-position to Fort Lauderdale, Fla., in the fall to offer alternating, seven-night Eastern and Western Caribbean voyages.

With its addition, Royal Caribbean has 25 ships.

USA TODAY in recent days received exclusive access to Harmony in advance of Sunday's first sailing with paying passengers. For our exclusive first photos of the ship's deck-top areas and interior, scroll through the carousel at the top of this story. Our first look at suites and cabins is below.