[Chinampas, artificial agricultural islands in Xochimilco, Mexico, photographed by flickr user Colibri.  The chinampas have been constructed in the lakes around Mexico City since pre-Columbian times; posts are driven into the lake bottom in shallows, connected into walls by weaving branches horizontally between the posts, and the resultant enclosures are filled with fertile soil from dredged by hand from the lake.  Rows of Ahuehuete, a willow, are planted along the edges, so that their growing root systems bind and reinforce the edges of the chinampas.  More recently, the chinampas have served as inspiration and model for the use of constructed wetlands to treat wastewater in Xochimilco (pdf).]