This dry stone planter the students built during a workshop I ran in San Francisco nine years ago is made with the same lovely saucer shaped (some call it 'cow patty' shaped ) stone which we also used to create the Yoni Wall in Gualala (seen below from forty feet up)...
... and again to build the tree-bookended 'Test Wall' . Both walls were completed several years after that original workshop.
There is something marvellous about this material which the supplier calls Fantasy River Rock from Grass Valley California.
Unshaped, unworked, undressed stones like these, stacked either vertically or horizontally, convey a powerful feeling of timelessness. The walls feel like they have been there since antiquity.