Spiral helical stair, with circular base, made of corten metal. Helical central structure, diameter 320 mm, steps wrapped in a band, without junctions in view. Steps made by metal with tread in Botticino marble. Railings made of satin-finished stainless steel, composed by handrail diameter 33 mm, vertical two-plate-pillars and 5 rods diameter 10 mm.