Neom
This is arguably the most eye-catching of Saudi Arabia's megaprojects.
Located in the north-west of the country, the zone spans 26,500 square kilometres. Designed as a futuristic smart city, which will be powered by clean energy and have no cars or carbon emissions, it has various attractions under its umbrella.
The $500 billion giga-project will be treated as a country within a country, with its own economic zone and its own authority, meaning it will be separate from the rules that govern the rest of the kingdom.