Architect Kate Orff's hero is the oyster. She sees natural filters as a major agent of urban change. Bundled into beds and sunk into city rivers, oysters slurp up pollution (they thrive on things which are toxic to others) and make dirty waters clean -- creating an "oyster-tecture." Orff shares her vision for an urban landscape that links nature and humanity for mutual benefit.

She is principal of SCAPE, a landscape architecture and urban design office with projects ranging from a 1,000-square-foot pocket park in Brooklyn to a 100-acre environmental center in Greenville, SC, to a 1000-acre landfill regeneration project in Dublin, Ireland. www.urbanlandscapelab.org