Garden Construction
Construction of the garden wasn't only complicated by getting the water up to the top, but also by having to avoid having the liquid ruining the foundations once it was released. Since stone was difficult to get on the Mesopotamian plain, most of the architecture in Babel utilized brick. The bricks were composed of clay mixed with chopped straw and baked in the sun. These were then joined with bitumen, a slimy substance, which acted as a mortar. Unfortunately, because of the materials they were made of, the bricks quickly dissolved when soaked with water. For most buildings in Babel this wasn't a problem because rain was so rare. However, the gardens were continually exposed to irrigation and the foundation had to be protected.
Diodorus Siculus, a Greek historian, stated that the platforms on which the garden stood consisted of huge slabs of stone (otherwise unheard of in Babel), covered with layers of reed, asphalt and tiles. Over this was put "a covering with sheets of lead, that the wet which drenched through the earth might not rot the foundation. Upon all these was laid earth of a convenient depth, sufficient for the growth of the greatest trees. When the soil was laid even and smooth, it was planted with all sorts of trees, which both for greatness and beauty might delight the spectators.