The world's largest cruise ship has 20 decks, 7 pools and would cover almost 4 city blocks

The world's largest cruise ship — the size of almost four city blocks — is set to begin its maiden voyage Saturday as it leaves from the Port of Miami.

Royal Caribbean's Icon of the Seas runs nearly 1,200 feet (365 meters) from bow to stern.

The ship, which is leaving South Florida for its first seven-day island-hopping voyage through the tropics, was officially christened Tuesday with help from soccer legend Lionel Messi and his Inter Miami teammates.

"Icon of the Seas is the culmination of more than 50 years of dreaming, innovating and living our mission – to deliver the world's best vacation experiences responsibly," Royal Caribbean Group President and CEO Jason Liberty said earlier this week. "She is the ultimate multigenerational family vacation, forever changing the status quo in family travel and fulfilling vacation dreams for all ages on board."

The ship sets sail as Royal Caribbean's cruises are having a moment online. Since December, the company's 9-month "Ultimate World Cruise" has captivated — and confused — a following of avid watchers on social media.

Millions are following the journey through the eyes of the passengers, as they live and post their lives aboard a vessel they'll be on for nearly a year. If it sounds like a reality show, that's exactly what some watchers have turned it into.

When the Icon of the Seas was first revealed in October 2022, the ship spurred the single largest booking day and the highest volume booking week in Royal Caribbean's then 53-year history, according to the cruise line.

The Icon of the Seas is divided into eight neighborhoods across 20 decks. The ship includes six waterslides, seven swimming pools, an ice skating rink, a theater and more than 40 restaurants, bars and lounges. The ship can carry up to 7,600 passengers at maximum capacity, along with 2,350 crew members.

It is powered by six dual-fuel engines, which can be powered by liquefied natural gas (LNG), a fuel alternative that the Cruise Lines International Association says reduces sulfur and greenhouse gas emissions. However, some environmentalists worry LNG-powered ships increase methane emissions. Other say that vacationers generate eight times more carbon on a cruise than they do on land.

Royal Caribbean says every kilowatt used on the Icon of the Seas "is scrutinized for energy efficiencies and emission reductions."