Abu Dhabi has started to build what it says is the world's first zero-carbon, zero-waste car-free city.
Masdar City will cost $22bn (£11.3bn), take eight years to build and be home to 50,000 people and 1,500 businesses.
The city will be mostly powered by solar energy and residents will move in travel pods running on magnetic tracks.
Abu Dhabi has one of the world's biggest per capita carbon footprints and sceptics fear Masdar may be just a fig leaf for the oil-rich Gulf emirate.
Others fear Masdar City - on the outskirts of Abu Dhabi City - may become a luxury development for the rich.
The project is supported by global conservation charity, the WWF.
Less power, less water
The city will make use of traditional Gulf architecture to create low-energy buildings, with natural air conditioning from wind towers.
Water will be provided through a solar-powered desalination plant, Masdar says. The city will need a quarter of the power required for a similar sized community, while its water needs will be 60% lower.
An artist's impression of a Masdar City transport pod
The city forms part of an ambitious plan to develop clean energy technologies.
In January, the government of Abu Dhabi announced a $15bn five-year initiative to develop clean energy technologies, calling it "the most ambitious sustainability project ever launched by a government".
As part of the plan, Abu Dhabi will become home to the world's largest hydrogen power plant.
The money is being channelled through the Masdar Initiative, a company established to develop and commercialise clean energy technologies, and Abu Dhabi hopes it will lead to international joint ventures involving much more money.
Abu Dhabi will invest $4bn of equity in the project and borrow some of the rest, Masdar said.
"We are creating an array of financial vehicles to finance the $22bn development," Masdar chief executive officer Sultan al-Jaber told Reuters news agency.
"We will monetise all carbon emission reductions... Such innovative financing has never been applied to the scale of an entire city."