The keel laying marks a milestone in the development of the ship, signifying the beginning of its physical construction.
During the ceremony, a 1,000-ton block measuring 32-ft by 154-ft (10 x 47 meters) was lifted by crane into the building dock.
Still to be named, the fourth Oasis-class ship will be delivered in spring 2018.
The Miami-based Royal Caribbean International sails 23 cruise ships to the destinations in Bermuda and the Caribbean, Europe, Canada and New England, Alaska, South America, Asia, and Australia and New Zealand.
Source: World Maritime News