This 3,647-guest vessel, christened by the late, Queen Elizabeth II in 2015, is P&O Cruises' flagship. Designed by world-class interior design experts, Britannia has a stylish palette of black, cream, and bronze with hints of blue that give it a clean, crisp aesthetic. Passengers get their first sense of the dramatic architecture as they enter the three-deck atrium with its elegant, sweeping staircase dominated by "Star Burst" — a gorgeous art installation that's part sculpture, part chandelier. The ship underwent a minor refurbishment in late 2019.