verticality height and upward movement

It is an enormous feat for one man to realize what Simon Rodia has built. he was not an engineer and most probably did and could not make the structural calculations. Nor can a spider calculate how to build its web. So Sam must have had the natural gift for knowing which step should follow the previous. These towers are not just buildings made by laying one stone upon the other, which in itself can also lead to catastrophe - these are the bare structures consisting of the minimal material necessary to hold themselves up and at the same time function as scaffolding for Sam. With scaffolding like this no building is needed.

It is very interesting to see the bubble-like shapes which follow the left tower while it tapers to the top. They are not only embellishments but contribute to the structural strength of this, the tallest of the towers.