Sustainable City outside Dubai, UAE. Dubai Sustainable City

For much of the 20th century, the United Arab Emirates was known as one of the world's biggest oil producers and, as a result, greenhouse-gas emitters.

But in the past two decades, the UAE government has made an effort to lower its own dependency on fossil fuels, shifting toward more environmentally-friendly sources to power its cities.

The UAE aims to have 75% of Dubai's energy come from clean sources by 2050. If the city pulls that off, it would have the smallest carbon footprint in the world.

As part of this larger goal, local company Diamond Developers is building a city 18 miles outside central Dubai that's designed to produce more energy than it consumes. Called Sustainable City, the development is expected to cost $354 million and be fully complete by 2019.

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