SAN FRANCISCO -- Silicon Valley's biggest city yesterday mandated green building standards for all new construction.

The San Jose City Council voted 9-0 to make all new housing developments save energy and water during the construction phase. The "Private Sector Green Building Policy" calls for new commercial, industrial and residential construction to increase energy efficiency, use less water, incorporate recycled water and divert waste from landfills, in addition to encouraging use of mass transit.

Architects and urban engineers around the world are building cities designed to cope with a future of growing populations, increasingly scarce resources and the need to reduce carbon emissions.

Adjacent to the Abu Dhabi airport in the United Arab Emirates, engineers are working on Masdar, a carbon-neutral, zero-waste walled city. The city is most notable for its total lack of automobiles, focusing instead on a public transportation system based on magnet-guided electric vehicles.

LAS VEGAS -- This city of lights and splashing fountains in the middle of the desert is drawing hundreds of people from around the world. They're not coming for the entertainment or for the casino gambling. They're trying to find answers to one of the biggest questions facing the world today: how to live more sustainably.

And they are turning to Wal-Mart -- the world's largest retailer -- for solutions.