Spiral stairways supported by a central column

Full Title

Stairways, ramps, or like structures (mounting or marking-off stairways E04F21/26; of temporary construction E04G27/00; means for facilitating access to swimming pools E04H4/144; ); Balustrades; Handrails (ladders permanently attached to fixed structures E06C9/00) > Stairways; Layouts thereof > characterised by the supporting structure > Spiral stairways supported by a central column