I just ran across these garden styles tonight and I'm so excited to try them!
Keyhole Gardens were started by the charity Send a Cow. They are a raised circular bed with a compost and water system in the center. An open wedge allows access to the compost and water reservoir as well as the inner area of garden. This style not only allows someone that can't, or in my case, doesn't want to bend over or kneel on the ground, but this is also an incredibly efficient method of gardening. It allows a whooping 64% of the garden area to be cultivated. A typical square bed uses only 24% once access around the perimeter is accounted for. Additionally, the top of the garden is sloped allowing a greater garden area than a flat garden. Want more? Of course you do! Having a center area for compost means it's all in one place. If space is at a premium in your yard, you wouldn't even need a separate compost pile. And for my use, it would be easy to add an umbrella for shade simply by sinking a PVC pipe into the ground near the center of the wedge.
Photo courtesy of amberdc on flickr, license applies
Gardening Tips & Ideas says, "The herb spiral is a permaculture gardening method that uses nature to its full potential. Gravity allows the water to seep through the levels meaning that the plants at the top get full drainage while the ones at the bottom may reside in a simple bog. It also gives your herbs shady spots with varying degrees. The herbs that need full-sun can be grown in those positions while more shade loving plants can be located on the opposite side." Again, this method of gardening allows for greater soil surface area since you are dealing with a slope. Veggies and ornamentals would be neat too. I think I may use it for succulents as well. You could get really fancy with this. Add a fountain to the top, or a bird bath, or just a landscape light. Endless possiblities!