Royal Caribbean's Allure of the Seas

When Royal Caribbean's Allure of the Seas hit the waters last year as the largest cruise ship afloat, it was simply the latest manifestation of the industry's "build it bigger and they will come" philosophy. Towering 16 stories with 2,700 staterooms, the ship became its own port of call with separate "neighborhoods," 26 dining options, name-brand retail shops, a merry-go-round and even an onboard park.

Allure has a wealth of wow factors that would be tough to offer on a smaller boat. Take a ride on the hand-painted, full-size carousel in the Boardwalk neighborhood, where you can pick up vintage candies you may not have seen for sale for 40 years. Or a zip-line ride, where guests are suspended 9 decks high and speed diagonally across the ship's open-air atrium.

The Allure's jaw-dropping interior "Central Park" space fools you into thinking you're outside with a mock sky above, a walkway flanked by trees, flowers, park benches, several bars and patios to stop for a drink or bite, including the line's fine-dining restaurant, 150 Central Park, and its Vintages wine bar. Meanwhile, there are a bedeviling number of stateroom types (37). With such an array of features, megaships like Allure are well-suited to multi-generational family travel (a growing trend) and mixed-group sailings.

It's appeal stretches across a wider demographic group, one that previously might have splintered off to multiple ships and that gives it a fighting chance to fill those 4,000 rooms.