The spiral
Probably a permaculture classic. Perfect place to get a grasp of the concept.
Increases edge: vertical space on the walls of the spiral increase the growing area each plant can have, warms roots more easily.
Creates microclimates: The top plants will get most of the sun but will also be the dryest. Bottom plants, by the pond, will be in the dark and wet, but will enjoy the night heat stored by the water. East side will get the morning sun, for those who dont like the long cold night. The south can grow peppers while the north tender lettuce.
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Companion planting: With rain, nutrients will leach, leaving the top plants with a poorer soil, and high fertility at the bottom. Plants will also attract beneficial insects such as pollinators, provide each other with different types of nutrients and influence flavours. and in the same line… The scaffold bed
This structure is made out of scaffolding and inclined cut oil barrels. The bottom is planted with a variety of basils and pepper plants while the top is home to aubergines, chillies and thyme. The middle shelf is good for lettuces and other greens. The sides would look great with beans or other climbers. The growing garden bin |
In cities, horizontal space is limited, but vertical ones are in abundance. 
Make holes at the bottom of a barrel and fill it up with any green material, manure, hay… urinate in it in the first few weeks. Add more material and a layer of soil when the bin contents have shrank. Squash love it if it contains lots of manure. Try growing tomatoes at the base of the barrel on the south side and lettuces on the north face. 
A variation would be to make slits on the side of the barrel and growing strawberries or vining plants.