A 75-mile-long desert skyscraper clad in mirrors will have its own high-speed railway, a sports stadium and vertical gardens where vegetables are harvested by robots.

Leaked architectural designs claim that Mirror Line, an entire city of five million people built on stilts as high as the Empire State Building, will be the largest structure in the world and have to “bend” to the curvature of the Earth.

But the building – developed at the whim of Saudi Arabia’s powerful crown prince – may not see the light of day as Mohammed bin Salman’s futuristic Neom megacity being built on the Red Sea coast is beset by hitches as officials scramble to keep up with his wildly ambitious visions.

The Mirror Line is mooted to cost around $1trillion and has no set completion date, but experts think it would likely take as long as 50 years. The kingdom is vastly rich and is currently enjoying a massive windfall revenue from high oil prices.

Not all of Saudi Arabia’s dream construction projects are completed. The planned world’s tallest skyscraper was put on hold after the last oil boom petered out.

The Mirror Line is just one part of the wider Neom development that the crown prince, 35, known as MBS, hopes will attract foreign investment into the kingdom to diversify its economy away from oil.

Read more: The Telegraph