Costa Serena has 1,500 cabins, 575 of which have a balcony and 28 of which are designed for disabled guests.
Decor is calmer than elsewhere onboard, with warm woods and blue and apricot colours. My standard balcony cabin was a decent size -- 220 square ft. -- and laid out exactly like the cabins on the newer Carnival ships. Two big mirrors give a further illusion of space. One has a decoration of coloured Murano glass smack in the middle where your face would be if you're anything over five feet six. There are no bathroom amenities at all apart from soap and shower stuff, although you can ask for shampoo and moisturiser.
Top marks for the 99 beautiful Samsara Spa cabins and suites, highly recommended if you plan to make good use of the spa. These have bamboo-effect doors and restful decor -- orchids in vases, calming colours combined with more sumptuous bedding than the standard cabins, as well as eco-cotton bathrobes, herbal teas and a lovely box of Elemis goodies in the bathroom. The spa cabin package includes a welcome consultation, two spa treatments, two classes, two tanning sessions, dining in the Samsara restaurant and unlimited access to the thermal suite.