As Saudi Arabia continues to develop as a tourist destination, it's making plans for big things -- specifically, one of the world's biggest airports.

The King Salman International Airport, due to be built in capital Riyadh, will have no fewer than six parallel runways, allowing 185 million passengers to pass through annually by 2050, reported CNN.

Built over the current King Khalid International Airport, it will sprawl over a whopping 22 square miles and is due to be designed by starchitects Foster + Partners, who have dubbed it an "aerotropolis."

In fact, Saudi Arabia already has form in the art of the aerotropolis -- it's already home to the largest airport in the world, King Fahd International Airport in Dammam, 250 miles northeast of Riyadh.

Luke Fox, Foster + Partners' head of studio, said the airport would "reimagine the traditional terminal as a single concourse loop, served by multiple entrances."

The site will include over 4.5 square miles of retail outlets, "residential and recreational facilities," and logistics space.

By 2030, the airport wants to be carrying 120 million passengers a year, before increasing by 50% over the following two decades. It plans to also handle 3.5 million tons of cargo per year by 2050. Seif A. Bahaa Eldin, a senior partner at Foster + Partners, said in a statement that the aim is for the airport to help Riyadh itself become a "global hub of creativity and innovation."

It hopes to be sustainable -- at least, as sustainable as a building serving the aviation industry can get -- with renewable energy and a LEED Platinum certification (Leadership in Energy and Environmental Design) in the plans.

An outside-in feel with lots of glass walls will connect people inside the terminal to the great outdoors.

CNN's Richard Quest, who visited Saudi Arabia this year, wrote in September that "Saudi is spending obscene sums of money creating new cities and tourist attractions" as part of its tourism drive. "I have seen countries change before, but I don't think I've ever seen anything quite like the change taking place in Saudi Arabia. It is not like the fall of Soviet Europe, nor the upheaval recently witnessed in Sri Lanka. Saudi's change is deliberate, deep-reaching and dramatic," he wrote.