The luxury liner is the biggest passenger ship ever built, rivalled only by its sister ship 'Oasis of the Seas', which will also visit Spain for three cruises from Barcelona this year after a refit in Rotterdam.
37,000 passengers have booked onto the Oasis, and it is believed that the ship's popularity helped to convince Royal Caribbean bosses to bring their 50mm-bigger and more technologically advanced flagship 'Allure' to the city long-term.
Completed in 2010, the 225,282-tonne Allure boasts a two-deck dance hall, a theatre with 1,380 seats, an ice skating rink, 7 distinct districts, plus 32 bars and restaurants including the first Starbucks coffee shop at sea.
6,296 passengers will also be able to enjoy an Aquatheatre (the deepest diving pool at sea), a park with 12,000 plants, two pools with wave machines to practice surfing, and performances of the musical Chicago.
They will be looked after by 2,384 crew members.
Over 500 workers will be needed to look after the ship and an estimated total 150,000 passengers during its stay in Barcelona, something the port's president says the city is "more than ready" to handle.
The Allure will Liberty of the Seas (339 metres and 4,300 passengers) as the largest ship in the Mediterranean.
It is expected to make trips to Palma de Mallorca, Marseille (France), and La Spezia, Civittachechia and Naples in Italy.
It will also make two stops in Malaga, one on its arrival in Spain from Miami and another when it leaves on a Caribbean cruise in autumn 2015.