Circular raised beds with a path to the center (a slice of the circle cut out) are called keyhole gardens. Often the center has a chimney of sorts built with sticks and then lined with feedbags or grasses that allows water placed at the center to flow out into the soil and reach the plants roots.
Urban gardening is now very popular these days because of food safety awareness, our financial economy, and because we want to be eco-friendly. Just because you only have a garden area that is very small does not mean you cannot use some small raised garden beds on a patio, deck, or back porch for some herbs, vegetables, flowers, or ornamental plants to enjoy.
You will have fewer problems with pests gardening in raised garden beds. If you have had previous problems with burrowing rodents, a lining of chicken wire in the bottom of each will eliminate them. Weed control is much easier handle because you can walk around a raised bed without having to bend over to pull out, if you have any weeds at all.
Spacing for anchors: Usable Length (in inches) / Total Length (in inches) * 12 inches. For my beds, I calculated a spacing of 11.75 inches for my 8 foot board by dividing the Usable Length of 94 inches by the Total Length of 96 inches and multiplying this by 12. My four foot boards require a spacing of 11.56 inches.