According to documents seen by The Wall Street Journal, the world’s largest structure will comprise two buildings up to 490 metres tall, running parallel for 120 kilometres.
The structures will be connected by walkways and a high-speed train will run beneath.
Following on the heels of the WSJ report, Saudi Crown Prince Mohammed bin Salman on Monday said The Line, in the kingdom’s $500 billion giga-project Neom, will “embody how urban communities will be in the future”.
Prince Mohammed announced the designs of The Line, which “puts human first, providing an unprecedented urban” living experience while preserving nature.
“The idea of layering city functions vertically, giving people possibility of moving seamlessly in three dimensions to access them, is a concept referred to as Zero Gravity Urbanism,” Prince Mohammed said.
The Mirror Line is designed by the US-based Morphosis Architects and the project involves at least nine other design and engineering consultancies.
They proposed building it in stages by creating 790-metre-long structures of varying heights up to 490 metres that will connect in a line.
The project builds on Crown Prince Mohammed bin Salman's announcement in January of plans to create a linear community that is expected to cost up to a trillion dollars and house about five million people when complete.
Prince Mohammed said the entire 170-kilometre coastal strip in the north-west of Saudi Arabia would be free of cars and streets, with zero carbon emissions.
The Mirror Line is one of a series of projects that make up Neom.
Four other developments, Neom Bay, Aqaba Region, Neom Mountain and Neom Industrial City, are intended to surround it.
There is also the planned project named the Vault which is a resort built into a mountainside.
Unveiled by Prince Mohammed in 2017, Neom is Saudi Arabia's flagship business and tourism development on the Red Sea coast and a central project in the 2030 Vision outlining the kingdom's plans to diversify the economy.
The development will include smart towns and cities, ports and enterprise areas, research centres, sports and entertainment venues and tourist centres.
It will be spread across 26,500 square kilometres and will comprise several zones, including industrial and logistics areas, all planned for completion in 2025.
People are expected to begin arriving in 2024, Neom's head of tourism said. The area is predicted to be home to millions by 2030.