I am really captivated with this design for an urban garden. When I was at school we studied anthropometrics or the body measurement percentiles, in order to design for a wide range of body dimensions. This was followed up for the more universally known expression, ergonomics or the study of worker’s bodies in relation to tasks. The idea is to make objects, products and processes that function well with the human form.
Besides designing a garden to fit the human scale, human movements there is the second reason I love this garden and that is the environment. This garden presumes a hostile, poor and even toxic environment. It can be place on a hard surface, even concrete. It builds into the garden all of the components for the chemistry and biology, the engines of soil production. Layer by layer these simple components like tin cans, clay chards, manure, wood ash are added to the mix.
The next reason is the wise use of water and waste to keep vital nutrients to feed the soil at the very core of the garden. With the central well for composting, watering easily accessible it assures greater success at maintaining the garden. It is designed overall to make it easy to successfully grown one's own food.
More sources here and here.