Amazing results. This is something I would love to have too.
The spiral represents constant changes in time and space. One thing always affects the next thing. It is the divine chaos which also establishes a perfect natural order for all existence. At least that is how I perceive the universe.
What amazes me more is the simple placement of the BBQ integrated in the garden for a simple family bonding and learning activity, is the spiral of ashes to earth to feed plants, to feed the fire, to cook the food, and returning again to the ashes. A wonderful way to harmonize one's needs while also honoring the needs of the land. Even the smoke in the air is a natural thing, as gases and minerals in the air cause the formation of warm clouds and rain to return these things to the thirsty soil.
RE: The mud & stone Spiral Wall (which is also a plant holder, BBQ & King's Throne)