To see pictures of the installation of this staircase, see the Sapis Rigging website. 

Spiral StaircaseA two-story, 1400 pound forged steel spiral staircase in the shape of a tree. Each step is supported by a different branch. 
Spiral Staircase 
Spiral Staircase
Spiral Staircase
Spiral Staircase
Spiral Staircase