This 2,218-guest ship marked the debut of Celebrity Cruises' Millennium class in 2000, meaning it’s now it the oldest ship in the cruise line’s fleet. Celebrity Millennium made waves for its cutting-edge, contemporary design, which included a 25,000-square-foot spa that is one of the largest and loveliest at sea. The whole ship is sleek and stylish and refurbishments, including a 2019 revitalization called the Celebrity Revolution that added elements found on newer Solstice- and Edge-class vessels, have kept the look clean and modern. The ship also features nine dining venues, six of which are complimentary.