San Francisco's Treasure Island, Calif.
Greensburg, Kan.

When a tornado blew through the tiny town of Greensburg, Kan. on May 4, 2007, nearly everything was lost including homes, businesses and trees. The roughly 1,500 residents are rebuilding Greensburg as one of the greenest towns in America, and the project has caught the attention of energy producers, among others. Discovery Communications and actor Leonardo DiCaprio are documenting the story of Greensburg's rise from the ashes in a TV series called "Eco-Town" on Planet Green.

Treasure Island's transformation to green is just another shade in its colorful history. The 400-acre (1.5-square-km) man-made island was built in the middle of San Francisco Bay for the 1939 Golden Gate International Exposition. The ­land was intended to hold an airport after the Expo. Plans for the commercial airport never took off, though, after the Navy acquired the island during World War II. In 1996, the base was decommissioned, and since then, the island has been home to a deteriorating landscape and about 3,000 residents.

­Under a new proposal, Treasure Island -- along with its neighbor Yerba Buena Island -- will become one of the most environmentally friendly developments in the United States when ground is broken in 2009.

The Treasure Island project will be a test bed for eco-friendly urban ideas. Some of the proposed green features include LEED-certified buildings, the reduction (or elimination) of storm water runoff, alternative forms of water treatment including artificial wetlands called Living Machines and a transit system that favors clean air vehicles over fossil-fuel chugging cars. A 20-acre (0.08 square-km) city-operated organic farm is planned in walking distance from the city center and will supply the projected 13,500 residents with locally produced foods. Solar and wind-farm power will provide energy; and by 2020, solar panels will cover 70 percent of rooftop space and will provide about 30 million kilowatt hours of electricity annually [source: ENN].