The so-called Hanging Gardens have plants above ground, and are cultivated in the air, with the roots of the trees above the tilled earth, forming a roof. Four stone columns are set beneath, so that the entire space through the carved pillars is beneath the ground. Palm trees lie in place on top of the pillars, alongside each other as beams, leaving very little space in between.
This timber does not rot, unlike others; when it is soaked and put under pressure it swells up and nourishes the growth from roots, since it incorporates into its own interstices what is planted with it from outside. Much deep soil is piled on, and then broad-leaved and especially garden trees of many varieties are planted, and all kind of flowering plants, everything, in short, that is most joyous and pleasurable to the onlooker. The place is cultivated as if it were tilled earth, and the growth of new shoots has to be pruned almost as much as on normal land. This arable land is above the heads of those who stroll along through the pillars. When the uppermost surface is walked on, the earth on the roofing stays firm and undisturbed just like a place with deep soil.
Aqueducts contain water running from higher places; partly they allow the flow to run straight downhill, and partly they force it up, running backwards, by means of a screw; through mechanical pressure they force it round and round the spirals of the machines. Being discharged into close-packed, large cisterns, altogether they irrigate the whole garden, inebriating the roots of the plants to their depths, and maintaining the wet arable land, so that it is just like an evergreen meadow, and the leaves of the trees, on the tender new growth, feed upon dew and have a wind-swept appearance. For the roots, suffering no thirst, sprout anew, benefitting from the moisture of the water that runs past, flowing at random, interweaving along the lower ground to the collecting point, and reliably protects the growing of trees that have become established. Exuberant and fit for a king is the ingenuity, and most of all, forced, because the cultivator's hard work is hanging over the heads of the spectators.