very interesting article:
In the year 2108, after the general collapse of society, Washington residents will flee the violent decay of the city and migrate to utopian "ecohubs" in the middle of the Potomac River.
There, civilization will be reborn amid renewed natural resources, wind- and solar-generated power, clean water and man-made wetlands brimming with wildlife.
Or, a century from now, Washington will be ringed by 2,000-foot towers -- erected on the sites of 28 Civil War forts -- where rain will be collected for water, power will be generated by wind and sunlight, and multitiered hydroponic farms will grow food for the city.
By 2108, heat could be generated by thermal wells. Cars and commuting could be obsolete. The Pentagon might be a peace institute. And elevated farms could grow crops above inner-city neighborhoods.
http://www.washingtonpost.com/wp-dyn/content/article/2008/01/15/AR2008011503407.html?nav=hcmoduletmv