Concept designs have been revealed of Saudi Arabia’s proposals for a linear smart city that would effectively be a 170km-long skyscraper.

Crown prince Mohammed bin Salman last year set out an initial vision for the project, named the Line, in Saudi Arabia’s north-west. However the project has been in development for several years.

This week’s design update says the project, eventually expected to accommodate 9 million residents, would occupy a footprint of just 34 square kilometres because the width of the development would be 200m. It would rise to 500m above sea level.

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