This stair, which I designed and built in my own apartment, had to fit within a very tight space. It is essentially a spiral stair, the central column of which is partially angled to adapt it to a rectangular floor opening. It may not meet Spain’s stringent building code, but it is nevertheless comfortable to use.
Rafael Gómez-Moriana 
Nice. Can you give us some dimensions? How large is that tight space? (I would guess about 2m by 2m, and height of 3m?)What is the size of each step?
The existing conditions were an opening in the upper floor of 2,20 x 0,72 m, and a floor-to-floor height of 2,87 m. The overall plan dimensions of the stair: the long segment of the “L” shape measures 2,20 m; the short one 1,27 m. The stair has 14 risers at 20,5 cm, while the average tread dimension is 23 cm.
Looks GR8…and functional as well.