Thousands of people lined the quays at Saint-Nazaire in western France and points along the coast to watch the Harmony of the Seas finally leave the shipyards, headed for the British port of Southampton from which it will start its official maiden voyage to Barcelona on 22 May
The boat, built for US-based Royal Caribbean Cruises Ltd, cost nearly one billion euros and its statistics are impressive:
At 362 metres, it is longer than the Eiffel Tower (324 metres);
At 46 metres, it is wider than the Arc de Triomphe (45 metres);
At 226 tonnes, it is five times the volume of the Titanic;
At 600,000m², its 16 decks are the equivalent of 84 football fields;
It can carry 6,360 passengers and 2,100 crew, more than 34 Airbus A340s.
The boat is credited with causing a boom in tourism in Saint-Nazaire, 95 percent of which was destroyed by bombing during World War II.
Guided tours of the STX France shipyard have risen 77 percent since the beginning of the year compared to the same period last year and had already risen 60 percent in 2015 with 40,000 paying visitors.
Cruise ships are controversial in the Mediterranean, however.
Venice imposed a ban on them in November 2014, claiming that they were "crushing the life" out of the city, although Italian authorities overturned it in January 2015.
And a recently published Atlas of Toxic France named them as a major factor in giving Marseille the most polluted air in the country.