For the spiral towers on this page 2 methods to spiral are used. The first is placing round units in an off-set position following a big circle, obtaining the king of spiral there is in a spring. This spiral can also be called a circular helix. For example, DNA is a double helix. The other way to construct a circular spiral is by slightly rotating units around their central axis and placing them on top of each other. This results in a structure that can generally be built much taller.