The Saudi government has announced it will spend $22bn (£14bn) on a metro system for the capital Riyadh.
Officials say the project, said to be the largest public transport initiative in the world, will have six lines and will help boost the economy.
Among the winning designs for the main stations were those of the Iraqi-British architect Zaha Hadid.
Construction on the metro will begin early next year, with the trains running by 2019.
The president of the Arriyadh Development Authority (ADA) Ibrahim bin Mohammed al Sultan said the Riyadh Public Transport Project will be "a major driver of employment and economic development".
He called it a "cornerstone" that would "enhance the quality of life" for Riyadh's population of nearly six million.
Cambridge University Gulf expert Jim Krane told the BBC that the metro made sense for Saudi Arabia.
"The Saudi government has a liquidity problem - the price of oil has been high but returns on investment in the foreign market are low," he said.
"So there's lots of cash and the need to spend it. What better way to do that than on infrastructure?"
The Riyadh metro, with more than 180km of track, will dwarf Dubai's metro.
Mr Krane, author of Dubai: The Story of the World's Fastest City, says the Saudi government has long viewed Riyadh as the potential capital of a unified Gulf region incorporating the current six nations of the Gulf Cooperation Council (GCC).
"The Saudi argument is that Riyadh is rather what Brussels is (to the EU) and a regional capital must have the amenities," he said.