Most furniture is less than three feet high.  If no humans are nearby, the airspace above such furniture is wasted.  For efficiency, this little 675-square-foot apartment hides an extra three rooms of furniture under the floor. The key is a 24-foot-diameter turntable.  The parts shown in color are beneath the main floor of the apartment, while the upper right quadrant forms part of the floor of the sunken great room, four feet lower than the rest.  At present a king-size bed is shown on this quadrant, which means that the great room is serving as a master bedroom.  Rotate the turntable 90 degrees to hide the bed, and the "lazy susan" brings in a couch and chairs, converting the great room into a living room.  Another quarter-turn brings in a formal dining table; another, hobby equipment. (TEXT CONTINUED BELOW) In the corners not required for the turntable, the extra under-floor space allows for storage beneath trap doors, air conditioning equipment, and even a sunken bathtub. The apartment's windows are on the left side of the plan (in the sitting room/second bedroom and in the kitchen's dining nook).  Between them is another window, small and high, which admits light to a shaft above the closet's lowered ceiling.  This white-interior shaft continues over the storage and coat closets, from whence the light enters the great room via clerestory windows near the ceiling as indicated by the little arrows. The great room measures 15 feet by 12 feet by 12 feet high.  Rooms this near to cubical have poor acoustics (ringing echoes), so some sound-deadening materials would be recommended for the outer walls.