Standing 165 m (541 ft) high along the river, the Iberdrola Tower is the latest great milestone in the process of transforming the city of Bilbao into a new cultural and business hub. The hall hosts an elegant architectural staircase - scope of the Permasteelisa Group work - its logarithmic spiral shape designed to look like a sculpture smoothly connecting the ground and first floors. The shape and the materials used all contribute to the sense of lightness and sinuosity. The staircase is composed of a suspended, curved steel structure covered by GRP (glass reinforced plastic) and runs from the ground floor to the first floor. The whole structure, and a portion of the first floor slab, is covered with white fiber glass cladding with a particular 'egg-shell' finish. All cladding appears as a single, continuous element without any visible joints. Even the low iron curved glass and the stainless steel handrail are connected to the steel structure without visible securing elements. The steps are covered by Travertine marble and illuminated by LED spotlights. The stairs and the tower itself have been designed considering the sustainability requirements envisaged for LEED^® certification. In fact, Iberdrola Tower is LEED Platinum^®.