Just a quick concept of a spiral staircase.
It was a pain to model. Yea you can get a step to array around an empty and spiral up like that but the wall that follows it up splays out in all directions and does not fit no matter what adjustment I made,
so I solidified it, applied the array then I put on a remesh modifier, twice, and smoothed it down and this was the result. Oh and symmetry on the Y axis as you can see.