Royal Caribbean has been an innovator in the mainstream sector of the cruise business over the past decade, transforming the architectural look and layout of big cruise ships and also rewriting the book on what's possible at sea: rock climbing, ice skating, boxing, surfing on deck, ziplining . . . what's next? The line's fleet includes some of the biggest cruise ships ever built, and while sheer size alone doesn't justify choosing these ships, the fact that Royal Caribbean puts the extra space to good use does justify it. These big ships really do deliver the goods in terms of variety, comfort, design, and amenities.