Oasis of the Seas can carry more than 6,000 passengers

The new Oasis of the Seas, a ship that eclipses the U.S. Navy's Nimitz-class supercarriers, will be the world's largest cruise liner when it makes its much-anticipated maiden voyage in December.

Under construction in Finland since 2006, the Oasis of the Seas is longer, taller, wider, heavier and more expensive than any other passenger ship ever built. It's five times the size of the Titanic and more than half again as large as the mammoth Queen Mary 2 — and it cost about $1.4 billion.

On its 18 decks, a crew of 2,165 will tend to as many as 6,296 paying customers, nearly 45 percent more than the largest cruise ships now operating, the Freedom-class vessels launched by Royal Caribbean three years ago.

But the Oasis of the Seas isn't just a jumbo version of its predecessors. More important than its staggering size is what its designers have done with the extra space: filled it with attractions never before seen on a cruise ship, including an open-air park with trees and hanging gardens, a boardwalk-style area with a merry-go-round, a pool that changes into a stage for high-diving shows and a theater that has booked the Broadway musical "Hairspray."

In short, Royal Caribbean has created a Las Vegas resort that floats — yes, there's a casino, too. Viewed up close from the outside, the ship doesn't seem like an industry game changer. It looks instead as if someone decided to stack an ugly imposing hotel or condos on the keel. But step aboard, and it immediately feels different.

Raimund Gschaider, the ship's "hotel" director, took me through the Oasis recently in Turku, Finland, where it's being built, including to Deck 5 where arriving guests will get their first glimpse of the inside.

Coming aboard the Oasis will be less like climbing onto a boat than like walking up the concourse of a fancy sports stadium. Instead of placing a block of cabins in the middle of the ship, the builders have stacked the rooms on either side, a radical innovation that left an airy, glass-enclosed atrium longer than a football field at the core.

Gschaider called it the Royal Promenade and pointed out stores, restaurants and the first cupcake shop at sea. And he led me up a few decks to the area dubbed Central Park where we stood under the sun in what felt like a plaza between two small apartment buildings, actually walls lined with cabin balconies.

The Promenade and Central Park are just two of seven "neighborhoods" on the Oasis. Two decks down and toward the stern is the open-air Boardwalk, complete with faux wood tiles, leading to a high-diving pool at the end of the ship. From the amphitheater-style seats, 600 guests can watch acrobatics and synchronized swimming with the ocean as a backdrop.

Nine decks up, atop the roofs of the cabins, is the Sports Zone, which might be described as a more traditional cruise ship's outdoor space if weren't for the size. I counted four swimming pools, two rock-climbing walls, a miniature-golf course, a jogging track, a basketball court, two water rides that simulate surfing, and a zip line you can buckle yourself into and glide along over the Boardwalk far below. Nearby are the luxury lofts, penthouses with a view of the sea that cost as much as $34,000 per week.

And somehow, below deck, the architects also managed to squeeze in a big children's play area, a sizable gym and spa, and an entertainment section with a theater, ice rink, casino, comedy stage and several nightclubs.

Carolyn Spencer Brown, the editor of the online site Cruise Critic, thinks the designers managed to make the Oasis feel both spacious and cozy. "I remember walking around it and forgetting I was on a cruise ship," she said in a phone interview. "The design is interesting because it tries to move people to every corner, with these separate, smaller areas."

Part of the appeal, I realized, lies in the knowledge that you're not just in a resort, but also in a marvel of engineering, an enormous, seaworthy craft that can cruise through the ocean at a speed of 22 knots.

From the stern, I could see its half-completed sister ship nearby in dry dock and look down into its mechanical guts. The ships are too big to be built the traditional way, from the bottom up, a deck at a time. Instead, pieces as large as buildings are finished on shore, then hoisted into place and welded together like so many Lego blocks. The Oasis took 181 blocks, each weighing about 600 tons.

Tor Olsen, one of the ship's captains, could barely contain his excitement as he showed off a high-tech bridge full of keyboards, joysticks and computer screens. Suddenly, I realized that we hadn't talked about the ship's Caribbean destinations, the stops in St. Thomas, St. Maarten, and the Bahamas, where harbors have been modified to accommodate the enormous ship.

"Our hope, of course, is that people don't get off, because this ship itself is the destination," Olsen said. "This is better than a lot of the islands."

But if the port calls don't matter, then why take a cruise at all? Why not just go to a resort in Las Vegas? "This is better than Vegas," Gschaider insisted.

Later, I spoke with Royal Caribbean president Adam Goldstein. "The challenge for our brand and for cruises in general is to fight for market share with land-based vacation options for all the consumer vacation dollars," he said. The Oasis was critical to the strategy, said Goldstein, because the vast variety of options it offers will destroy the popular myths that there's nothing to do on a cruise ship, or that cruises are only for older people.

Royal Caribbean is also hoping that the Oasis will be able to command a big price premium, significantly more than the $499 that many other ships charge for a seven-night Caribbean cruise.

But even at a higher price, Goldstein argued, the ship will be a bargain because it offers so much.

The cruise-resister in me still had concerns. How would it feel to be trapped on a boat with so many people? Gschaider said the Oasis is so big that there's more space per passenger than on other ships, and it will feel less crowded.

And what damage would such a big ship do to the environment?

Goldstein pointed out that the Oasis is equipped with the most advanced wastewater-purification systems and technology, which makes it much more energy efficient.

But environmentalists say that it doesn't do enough to reduce air pollution, and that a cruise ship will always burn more fuel than a land resort.