Hi. I used a stylized ouroboros symbol The vine with the open mouthed leaf or plant enclosing the city and the farm furrows and the blue sky.
Symbology behind the Ouroboros
The ouroboros has several meanings interwoven into it. Foremost is the symbolism of the serpent biting, devouring, eating its own tail. This symbolises the cyclic Nature of the Universe: creation out of destruction, Life out of Death. The ouroboros eats its own tail to sustain its life, in an eternal cycle of renewal.
In the above drawing, from a book by an early Alchemist, Cleopatra, the black half symbolises the Night, Earth, and the destructive force of nature, yin. the light half represents Day, Heaven, the generative, creative force, yang.
Alchemically, the ouroboros is also used as a purifying glyph.
Basically, it encompasses the circle, the cyclic nature of recycling and gardens and in a way recycling is "eating it's own tale" to produce something out of destruction. Etc.
Any input welcome. Please ask for variations if you would like to see any (font, color, additions, subtractions,etc). If you want to have a dialog on anything, using the private message feature really helps, since it allows me to directly respond to you to give information and you are notified there is a message, as opposed to posting something on my entries page and hoping you see it before the end of the contest (if at all sometimes). :-)
C