Fastest way do a spiral stair.

 From:  Grendel
11084.13 
Kind of off topic but this looks like poor design trying to cope with restricted footprint....definitely looks restrictive to users who are anything beyond 5'10" or so due to the center being tilted like that. Trying to move one floor vertically in the space of a small coat closet makes this seem like an after thought or one of those "tiny house" solutions....