Over four times as long as its nearest rival, the planned 'Freedom Ship' will sail the seven seas as an independent city-state operating outside the jurisdiction of any single nation

Royal Caribbean International’s twin cruise liners, Star of the Seas and Icon of the Seas, share the title of the world’s largest cruise ship. At almost a quarter of a mile in length, and with capacity for some 5,600 passengers each, these massive vessels are true ocean giants.

But put together, Royal Caribbean’s dual flagships would still be only half the length of a new “floating city” that’s currently in the planning stage. The £12bn Freedom Ship is set to have capacity for around 80,000 passengers and crew – with a full-sized hospital and schools alongside all of the usual cruise liner amenities – making it a true “floating city”.

A press release from parent company Freedom Cruise Line International states that the Freedom Ship will be the largest ship of any kind ever built: “The Freedom Ship concept has been developed over years of planning and in collaboration with naval and maritime experts as well as globally acclaimed architects.

“Weighing in at over 2 million gross tons, a mile in length, 800 ft wide and 30 stories tall, Freedom Ship would be the largest maritime vessel ever constructed in history.”

The monster ship, which is intended to have no home base and simply sail endlessly around the world powered by its onboard nuclear reactor, will have a concert hall, a convention centre, a water park and even a 15,000-capacity sports stadium.

The concept was originally floated in the 1990s by American engineer Norman Nixon. But development was stalled after his death in 2012.

Nixon envisioned a libertarian-leaning community operating largely outside the jurisdiction of any single nation. His early descriptions emphasised the ability to live, work and do business while remaining mostly in international waters.

The Freedom Ship’s permanent residents would effectively live in a city whose scenery constantly changes as it slowly circumnavigates the globe.

Efforts were made to revive the project from time to time following Nixon’s death, but in March this year Freedom Cruise Line made a major announcement about progress on the project, naming a project manager, a designer and a naval architect who will be working full-time on the hugely ambitious project.

Roger Gooch, chief executive of Freedom Cruise Line International, told The Telegraph that it’s now just a question of raising the £12bn budget: “We feel very confident that we can put this together, but the capitalisation is key,” he said.

Many of the facilities, such as the onboard nightclub and separate hotel facilities, could be leased out to independent businesses: “We want entrepreneurs to lease or buy space from us, just like they would in a land-based community,” Gooch explains.

The plan for the Freedom Ship is for it to exist as an independent floating city, with a resident community that constantly circles the globe. While today’s mega-liners have sparked fury in coastal communities because they flood port cities with unsustainably large numbers of day-trippers, the idea for the Freedom Ship is that it would be a destination in itself.

While the total capacity is set to be 80,000 people on board at any one time, there would only be around 50,000 permanent residents, with roughly 20,000 crew and scope for some 10,000 visitors.

“We want people to come out and enjoy the floating city while it’s in their area because it may not be back for another two and a half years,” Gooch says.

He added that there would be significant advantages to the Freedom Ship being an effectively stateless community that extended far beyond having a duty-free shop: “We also want a state-of-the-art hospital. We’ve been approached by medical research facilities because we would be outside the reach of regulatory bodies, so the Freedom Ship would be an ideal venue for that.”

Designer Kevin Schopfer explained that while the Freedom Ship would be the most massive ship ever to set sail, he hadn’t forgotten the importance of seeing it at a human scale: “We started with the view that the ship should not be a monolithic piece but visually comfortable, so we softened all the edges. We also want it to breathe, so we’ve gone to great lengths to allow walkways and green spaces.”

In addition to several miles of pedestrian walkways, there would be a tram system taking passengers from one end of the massive floating city to the other.

“We have a soccer pitch, too,” Schopfer added. “It’s not a massive stadium, but it could also be used for events and concerts. Taylor Swift came up in the discussion at one point, but I said I don’t know if we can handle that!”

Some sceptical experts have described the Freedom Ship as a beautiful but ultimately impractical megaproject. They cite issues with hull stress on a ship of such immense size. Ocean waves impose enormous bending forces on ships, and a vessel a mile long would experience unprecedented structural loads.

While much of the ship’s construction is expected to take place at sea, shipbuilding specialists point out that there is no dry dock on Earth large enough to cope with the initial stages of construction.

Once the ship is actually built, there will also be enormous technical challenges around food supply and waste management. The Freedom Ship's permanent population would be roughly equivalent to that of St Albans in Hertfordshire, with a similar requirement for infrastructure.

And of course there is the issue of cost. Nixon’s first estimate called for an investment of $6bn, but that figure has risen to roughly $16 billion (just under £12bn) today.