The world's largest cruise liner on Friday began its maiden voyage to Florida, gliding out from a shipyard in Finland with an amphitheater, basketball courts and an ice rink on board.

The 16-deck Oasis of the Seas spans 1,200 feet from bow to stern. Its 2,700 cabins can accommodate 6,300 passengers and 2,100 crew.

Commissioned by Royal Caribbean International, the ship cost $1.5 billion and took two and a half years to build at the STX Finland Oy shipyard in Turku, southwestern Finland.

The liner has four swimming pools, volleyball and basketball courts, and a youth zone with theme parks and nurseries for children. There is also an ice rink that seats 780 spectators and a small-scale golf course.

The Oasis of the Seas is due to make its U.S. debut on Nov. 20, when it will be unveiled on ABC's "Good Morning America" show at its home port, Port Everglades in Florida. The official naming ceremony will be 10 days later. The ship will embark on its first cruise — a four-day trip to the port of Labadee in Haiti — on Dec. 1.

The Oasis of the Seas left Finland's frosty shores on Friday and is set to exit the Baltic Sea on Saturday, when it must squeeze under the Great Belt Bridge between two Danish islands.

Even after lowering its telescopic smokestacks, the ship rises nearly 212 feet above sea level, while the bridge's vertical clearance is only 213 feet.

To be on the safe side, the ship will speed up so that it sinks deeper into the water when it passes below the road-and-rail link, said Lene Gebauer Thomsen, a spokeswoman for the operator of the Great Belt Bridge.

Mikko Ilus, project engineer at the Turku shipyard, said he didn't expect clearing the bridge to be a problem.

"Theoretically, of course it's possible, but the tidal variations in the Baltic are so small that it's unlikely," he said.

The enormous ship features various "neighborhoods" — parks, squares and arenas with special themes. One of them will be a tropical environment, including palm trees and vines among the total 12,000 plants on board. They will be planted after the ship arrives in Fort Lauderdale.

In the stern, a 750-seat outdoor theater — modeled on an ancient Greek amphitheater — doubles as a swimming pool by day and an ocean front theater by night. The pool has a diving tower with spring boards and two 33-feet high dive platforms. An indoor theater seats 1,300 guests.

Accommodation includes loft cabins measuring 545 square feet with floor-to-ceiling windows. There are also 1,600-square-feet luxury suites with balconies overlooking the sea or promenades.

One of the "neighborhoods," named Central Park, features a square with boutiques, restaurants and bars, including the "Rising Tide" bar, which the shipping line describes as "the first moving bar at sea."

It moves up and down three decks, allowing customers to get on and off at different level promenades.

Engineers at shipbuilder STX Finland said environmental considerations played an important part when planning the vessel, which dumps no sewage into the sea, reuses its waste water and consumes 25 percent less power than similar, but smaller, cruise liners.

"I would say this is the most environmentally friendly cruise ship to date," said Mikko Ilus, project engineer at the Turku yard. "it is much more efficient than other similar ships."

The Oasis of the Seas was due to call in at the English port of Southampton before continuing its voyage across the Atlantic.

STX Finland is building a sister ship — Allure of the Seas — for Royal Caribbean which is due to be launched in 2011.