Cruise ships have evolved from the type of craft television viewers remember from the Love Boat series to vessels capable of trans-Atlantic voyages. Until the advent of Sovereign-class cruise ships, cruise customers enjoyed a comparatively limited variety of amenities: deck chairs, swimming pools, shuffleboard, and various classes of accommodation and food options. Now ships have rock climbing walls, multi-story water slides, interior atria affording verandas to more staterooms … passengers have all of the comforts of home, all of their favorite activities, and often their favorite hangouts, such as Starbucks, as well.

Sovereign-class cruise ships, the first “mega-ships” built for the cruising market, have now been eclipsed by Royal Caribbean’s enormous Oasis-class vessels. These ships have 16 (or more) passenger decks, split atria, five-deck-high Central Park and Boardwalk outdoor areas, a Broadway stage, and space for over 6200 passengers. The enormous beam width — 154 feet at the waterline — accommodates all of these wonders, and more.

These new ships do not resemble classic cruisers; the multiplicity of decks in particular changes their profiles. Despite their somewhat ungainly appearance, these new models have not reached their maximum theoretical size. The main limitation, other than cost, is that cruise ship ports are too small to accommodate them.

The construction of these behemoths is, surprisingly, accomplished using multiple enormous prefabricated sections. The newest entry into Royal Caribbean’s Oasis-class fleet is the Harmony of the Seas, whose maiden voyage launched May 29, 2016. Total construction time for Harmony was an astonishingly modest 32 months.

This time-lapse video condenses the construction time into a few fascinating minutes.