Continuing tonight on Five is the documentary series that lifts the lid on some of the most incredible structures and machines in the world. Tonight’s episode looks at the engineering behind Freedom of the Seas – the largest passenger ship ever built.

When the colossal RMS Queen Mary II (QM2) superliner was completed in 2003, she was by far the longest, tallest and broadest ship of her kind ever built. But just three years later, the QM2’s crown was taken. Measuring a quarter of a mile in length and standing at a height of 18 storeys, Royal Caribbean’s Freedom of the Seas is the largest passenger ship in the world and a wonder of modern maritime science.

This week’s Megastructures reveals the technological secrets behind the creation of Freedom of the Seas. The story begins in Finland’s state-of-the-art Kvaerner Masa-Yards shipyard, where the world’s leading engineering minds first came up with the idea for such a leviathan. While the ship contains some of the cruise industry’s most amazing recreational features – including an onboard surf park, cantilevered whirlpools that extend 12 feet beyond the sides of the ship, a rockclimbing wall, a basketball court and an ice-skating rink – she also possesses imaginative onboard programming and cutting-edge technology.

Below deck, the engine room is packed full of technology, including a cutting-edge navigational system that guides the ship and its precious cargo through extreme weather and violent oceanic conditions. The power is provided by six V12 diesel engines that put out 75,600 kW – or over 100,000 horsepower – providing a top speed of 21.6 knots.

With Freedom of the Seas, the cruiseliner industry has reached a critical size – anything longer, taller or with a greater draught may not actually be possible. According to engineers, only an increase in the ship’s breadth would be physically feasible – and this only with major new scientific and technical breakthroughs. As it stands, the ship weighs in at some 160,000 tonnes and can carry up to 5,000 people, meaning that flotation is a delicate balancing act.

Freedom of the Seas is yet another major milestone in Royal Caribbean’s history of innovation. As this superliner comes to life, Megastructures provides a behind-the-scenes glimpse at one of the most sophisticated marvels of modern naval engineering.