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Â©2009 Diane Cook / Len Jenshel / National Geographic
A garland of nature crowns Chicagoâ??s City Hall, softening the hard edges of a town famous for steel and stoneâ??and lowering summer temperatures on the roof. Inspired by a worldwide movement, Mayor Richard Daley has made Chicago North Americaâ??s leading â??green roofsâ? city.