In 1843 Brunel's ironship Great Britain was launched, becoming the forerunner of the great steel-hulled ships of today. Yet she was tiny compared with the transatlantic liners of the early 1900s as ship-owners vied for the top spot in terms of speed, elegance and size. Liners such as Mauritania and Titanic were later followed by two giant Queens and France's liner Normandie. If the innovative engineers of the Victorian age guided the shipping industry from sail to steam, wood to iron and later to steel, then the twentieth-century invention of the computer took ship construction to entirely new concepts. Massive passenger vessels, equipped with remarkable facilities, efficient machinery and capable of meeting the highest standard of safety, can now be built from keel to funnel in no more than two years.

Construction techniques have changed beyond recognition, as have methods of ship design and, indeed, the very roles that these floating resorts are asked to play. Today Royal Caribbean's sister ships Oasis of the Seas and Allure of the Seas are the first passenger ships in history to exceed 200,000 gros tons and are promoted as offering a third more space than any other cruise vessel afloat and measuring seventy times the size of the first Victorian passenger-carrying ironship. For the foreseeable future, at least, these two giant floating cities will hold the accolade of being the biggest passenger ships of all time.