This is Masdar City in Abu Dhabi (Map). The idea is to build a 2.3 square mile city starting from desert based on zero carbon emissions standards. It's designed by Foster and Partners and is actually getting built. Some photos can be seen here (the better ones are near the end), and here's its wiki page.
Dongtan (great article) outside of Shanghai (Map). This is designed by Arup and looks like it isn't getting built.
Both of these cities propose to construct a more sustainable built environment by starting from scratch and avoiding the milieu of mistakes that generally plague typical development. It's a novel approach for sure, and the research done for Dongtan is incredible. Here's a bit from the Wired article on how density was determined for Dongtan:
"Their first decision was big. Dongtan needed more people. Way more. Shanghai's planning bureau figured 50,000 people should live on the site — they assumed a green island should not be crowded — and the other international architects had agreed, drafting Dongtan as an American-style suburb with low-rise condos scattered across the plot and lots of lawns and parks in between. "It's all very nice to have little houses in a green field," Gutierrez says. But that would be an environmental disaster. If neighborhoods are spread out, then people need cars to get around. If population is low, then public transportation is a money loser.
But how many more people? Double? Triple? The team found research on energy consumption in cities around the world, plotted on a curve according to population density. Up to about 50 residents per acre, roughly equivalent to Stockholm or Copenhagen, per capita energy use falls fast. People walk and bike more, public transit makes economic sense, and there are ways to make heating and cooling more efficient. But then the curve flattens out. Pack in 120 people per acre, like Singapore, or 300 people, like Hong Kong, and the energy savings are negligible. Dongtan, the team decided, should try to hit that sweet spot around Stockholm.
Next, they had to figure out how high to build. A density rate of 50 people per acre could mean a lot of low buildings, or a handful of skyscrapers, or something in between. Here, the land made the decision for them. Dongtan's soil is squishy. Any building taller than about eight stories would need expensive work at the foundation to keep it upright. To give the place some variety and open up paths for summer wind and natural light, they settled on a range of four to eight stories across the city. Then, using CAD software, they started dropping blocks of buildings on the site and counting heads.
The results were startling. They could bump up Dongtan's population 10 times, to 500,000, and still build on a smaller share of the site than any of the other planners had suggested, leaving 65 percent of the land open for farms, parks, and wildlife habitat. A rough outline of the city, a real eco-city, began to take shape: a reasonably dense urban middle, with smart breaks for green space, all surrounded by farms, parks, and unspoiled wetland. Instead of sprawling out, the city would grow in a line along a public transit corridor."
Why had no one done this before?
These cities are essentially huge experiments which require both a huge purse and some optimism that people will flock there. Which I think they will if they're done right, and of course if they're cost effective it'll be pretty incredible. My only reservation is that the cities are planned all at once which is both a blessing and a curse. The blessing being things like Masdar City's raising the entire city on concrete piers so that all transportation can take place underneath. This sort of design feature is only available if you plan everything beforehand, or at least it's many times cheaper to do so. The curse is a bit harder to explain, but it takes the same vein as a free market versus a socialist economic system type argument. It isn't easy to determine exactly what people are going to want in a city. Whole parts of it may fall into disuse if the preferences of future inhabitants aren't interpreted properly such as was the case with Boston's West End.It was demolished because it was considered a slum although not by residents. Yet it worked and people lived there in a functioning community whereas it was replaced by and urban renewal project that served few and was considered excessive.
I tend to think of cities as a sort of biological organism that is constantly growing, contracting, dying, and regenerating. The buildings are the cells, the streets the capillaries, the highways and subways the veins and arteries, and people the blood cells moving about bringing life to everything. I'm skeptical that any amount of planning can fully account for the complexity that time brings to the development of a city. Then again maybe if built small enough (Masdar City is not huge) it may be possible. Perhaps it can be expandable or maybe just the infrastructure could be built with zoning requirements similar to the New Urbanism ideas of Seaside, FL. Either way it should be interesting to see how these perform as they come online.