The form, volume and structure of the towers is generated by two ellipses, one at foundation level and the other at a horizontal plane at . These two ellipses are rotated relative to another. The tightening caused by the rotation between the two ellipses forms a "waist" and a densification of material halfway up the tower. This means that the lattice structure, which at the bottom of the tower is porous and spacious, becomes denser at waist level. The waist itself becomes tight, like a twisted rope; transparency is reduced and views to the outside are limited. Further up the tower the lattice opens again, accentuated here by the tapering of the structural column-tubes.